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FRANKLIN INSTITUTE LIBRARY 
PHILADELPHIA, PA. 


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Whpsical and Chemical Examination of 
Waints, Varnishes, and Colors 


By HENRY A. GARDNER 
Director Scientific Section, Educational Bureau 
Paint Manufacturers’ Association of the 
United States; National Varnish 
Manufacturers’ Assocta- 
tion, Co-operating 


SECOND EDITION 


Institute of Paint and Warnish Researeh 
Washington, BD. C. 


at me Pi ‘ Es 
COPYRIGHT — 
BY H. A, GARD 
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DEDICATION. 


To the HON. HERBERT HOOVER , 
U.S. Secretary of Commerce 


Under whose helpful engineering guidance and en- 

couragement, many problems have been solved by 

workers in the industry, this volume is respectfully 
dedicated. 


Chapter 
No. 

I 

II 

III 

IV 

Vv 

VI 

VII 

VIII 

IX 

xX 

>. 

XII 

XIII 

XIV 

XV 

XVI 


XVII 
XVIII 


XIX 
XX 
XXI 
XXII 
XXIII 


XXIV 
XXV 
XXVI 
XXVII 
XXVIII 
XXIX 
XXX 
XXXI 
XXXII 
XXXII 
XXXIV 


XXXV 
XXXVI 
XXXVII 
XXX VITI 
XXXIX 
XL 

XLI 

XLII 
XLIII 


CONTENTS 


Page 
Physical Examination of Paint Materials... 9 
Pfund Paint Testing Instruménts| 273.0 19 
A. Study of Color Systems...<.. i 34 
Plasticity and Yield Value......0.5.. ee ee 48 
An: Experimental Drying Time Meter gee 56 
A Color Change Cabinet... jesse 61 
Use of the Microscope in Examining Paint Films... 64 
Hardnesa of Films... 00002 68 
Accelerated Testing Cabinets..ci0 205 = ves 
Determining the Specific Gravity of Pigments... 81 
Determining the Fineness of Paint Pigments... 91 
Oil “Absofptioh: of Pigments....40 a) 107 
Texture of Pigments......:2.) 5 118 
Testing the Light Resistance of Lithopone. 123 
Viscosity of Varnishes.................. sncnsur nts stop aay gic a ee le 149 
Surface Tension and Interfacial Tension of Varnishes and 
Parimt Ligue cccace cesscc sss en etre 54 
Color Standards. for Varnishes..2.22.0)00. 2 163 


Testing the Speed of Evaporation of Thinners for Paint 


and Varnish. Films... 072s 169 
Examination of Turpentine and Mineral Spirits....................... 175 
Testing Aluminum. Stearate... 181 
Suggestions for Making Exposure Tests .e.cccccccccccccccccewseccseseueee 193 
Testing Colors for Tone and Strength. 206 
Routine Testing Methods for Physical Properties of White 

I 2441-54 H-NET oe 210 
Analysis of Paints and Paint Vehiclesi... eee 213 
Analysis of Paint Oils.uuoc 2s ee 218 
Examination of Flaxseedic..2 2 237 
Tentative Specifications for Raw Tung Oil 2, 239 
Analysis of Varnish......U0 2 BERNE A Sips PANY Sea 246 
Analysis of Mixed Driers...) 255 
Examination and Analysis of Varnish Resins... 0.0... 258 
Tentative Method. of Testing Shellac 267 
Testing Insulating Varnishes....3 cee 276 
Analysis of Pyroxylin Lacquer’ Coatings eee 283 
Bituminous Paints, Varnishes, Cements, and Similar Ma- 

23 SE (ARTO 2938 
Analysis of White Paint Pigments... eee 304 
Analysis of Lead Oxides.....2) gee 333 
Analysis of Vermilions).....00 000 eae 347 
Analysis of Indian Reds and Red’ Oxides... 351 
Analysis of Ochers.2. i i.-cjccivesstoiecn cea eee eer: 355 
Analysis of Yellow and Orange Pigments.......ueee 358 
Analysis of Blue Pigments...) ee 362 
Analysis of Green Pigments... 368 
Analysis of Black Pigments........... es 370 


PREFACE. 


The character and suitability of varnishes can best be judged 
from physical tests. The properties of many pigments and oils 
are learned through similar means, and in this manner informa- 
tion may be gleaned that is often far more useful than that af- 
forded by chemical analysis. In a similar manner, physical tests 
of paint are rapidly being developed that may ultimately make it 
possible to predict the serviceability of various products. In 
this volume, therefore, an attempt has been made to outline or at 
least refer to the more important physical tests that every paint 
and varnish laboratory should be familiar with. Physical tests 
previously published in Scientific Section Circulars have also 
been abstracted for presentation. 

Methods are given for the analysis of paints, pigments, oils 
and similar products. The more important methods adopted by 
the American Society for Testing Materials (see reports of 
Committee D-1, A. S. T. M., 1916-1923), as_ well as_ several 
methods privately communicated, are also contained in the 
present volume. A large amount of important material here- 
tofore unpublished is also added. This includes methods for the 
analysis of organic red colors; bituminous enamels, varnishes 
and cements; examination of lacquers; analysis of mixed driers; 
physical and chemical assay of colors; optical examination of . 
white pigments with tables giving their spectral composition and 
relative hiding power, etc. 7 

Due to the great dissimilarity of specifications for paints and 
varnishes previously used by the various departments of the 
United States Government, a member of the War Service Com- 
mittee of the Paint Industry suggested early in 1918 that steps 
be taken to inaugurate a plan for correlating all the specifica- 
tions of the various departments into a series of specifications 
that would be acceptable to all. This idea undoubtedly led to the 
formation of the Federal Specifications Board, of which the 
writer is a member, whose labors have resulted in specifications, 
which have been bound into this volume. 

To the following the writer is indebted for material or sugges- 
tions in the preparation of this book: P. H. Walker, L. L. Steele, 
F’. W. Smither, E. F. Hickson, E. H. Berger, and I. M. Jacobson, 
all of the U. S. Bureau of Standards; J. A. Schaeffer, A. H. 
Pfund, L. E. Barton, F. G. Breyer, P. R. Croll, Harley A. Nelson, 
me erown, P. H. Butler, R. E. Coleman, P. C. Holdt, H. C. 
Parks, and other associates. 

HENRY A. GARDNER. 

Washington, D. C., January, 1925. 


ti 


CHAPTER I. 
PHYSICAL EXAMINATION OF PAINT MATERIALS. 


There is given below a series of physical methods by which 
the character of various pigments, colors, oils and similar prod- 
ucts may be judged. For the chemist who desires to become 
familiar with the work of other investigators of the physical 
properties of these materials, the following references are given. 
Abstracts of some of these articles are, however, included in 
this volume. 


Optical Properties and Theory of Color of Pigments and Paints—H. E. 
Merwin. Proc. Amer. Soc. Test. Mater. XVII—Part II, 494. 

Determination of Absolute Viscosity by the Saybolt Universal and Engler 
Viscosimeters—Winslow H. Herschel. Jbid., 551. 

The Standard Saybolt Universal Viscosimeter—Winslow H. Herschel. 
Ibid... X VIII—Part II, 363. 

The Variable Pressure Method for the Measurement of: Viscosity—E. C. 
Bingham. Ibid., 378. 

Paint, a Plastic Material and not a Viscous Liquid: the Measurement 
of its Mobility and Yield Value—E. C. Bingham and Henry Green. Ibid., 
XIX—Part II, 640. 

An Instrument for Measuring the Hiding Power of Paints—R. L. Hallett. 
Ibid., XX—Part II, 426. 

A New Colorimeter for White Pigments and Some Results Obtained by 
Its Use—A. H. Pfund. JIbid., 440. 

Further Development of the Plastometer and its Practical Application 
to Research and Routine Problems—H. Green. Ibid., 451. 

Stress-Strain Measurements on Films of Drying Oils, Paints and Var- 
nishes—H. A. Nelson. Jbid., XXI, 1111. 

The Use of Secondary Reference Standards in Process Problems of 
Color Measurement—H. S. Busby. Jbid., 1139. 

Relation of Yield Value and Mobility of Paints to Their so-called Paint- 
ing Consistency—J. E. Booge, E. C. Bingham, and H. D. Bruce. Ibid., 
XXII. 

Some Physical Properties of Paints—P. H. Walker and J. G. Thompson. 
Ibid., XXII. 

Accelerated Weathering of Paints on Wood and Metal Surfaces—Harley 
A. Nelson. Jbid., XXII. 

An Analysis and Comparison of Systems of Color Measurement and 
Some Notes on Interchangeability in Color Measurement—H. S. Busby. 
Pot... X AIT. 

An Application of the Pfund Colorimeter to the Determination of Tinting 
Strength—J. A. Calbeck. Jbid., XXII. 

Hiding Power of Paints—R. L. Hallett. Jbid., XXII. 


Physical Character of Films.—Laboratory methods for de- 
termining the physical properties of paint and varnish films are 
very much to be desired. The field is of great importance on 
account of the growing tendency of specification writers to set 
requirements for varnishes almost wholly on physical properties, 

9 


= 


10 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


allowing the varnish maker to use whatever material he finds 
best suited to produce products that will meet the requirements. 
Certain physical properties, however, are difficult to define. For 
instance, requirements for such characteristics as hardness, 
elasticity, and gloss should be made definite, so that the manu- 
facturer may check up his products as closely as he might by a 
chemical analysis of an oil paint. The field opened up by such 
work is a wide one, and so far but little explored. Excellent 
work, however, has been done during the last few years by 
Breyer, Pfund, Bingham, Green, and Hallett, and it is under- 
stood that these investigators are now making further progress 
along similar lines.* 

In 1908 probably one of the first efforts to devise and definitely 
define physical tests on paint films was made in the old labora- 
tories of the Scientific Section and published in the First Annual 
Report of the Section (1908). In this report, methods of pre- 
paring paint films were outlined and apparatus for determining 
the tensile strength (Perry filmometer), as well as methods for 
determining opacity, permeability, effect of weathering, etc., 
were described. Difficulty was had, however, in some cases with 
the preparation of films of suitable size and in preserving them 
for experimentation. While open to criticism from many angles, 
this early work was productive of much information. 

With a view to resuming this work and of making a further 


study of the possibilities along this line, the writer has recently 


completed a series of tests which indicate that films may 
be made on a standardized form of bond paper and tested with 
much less difficulty than when formed on gelatinized or mer- 
curized metal and stripped therefrom, as in the early experi- 
ments. 

In the new tests a series of paints and varnishes were applied 
in two coat work to a bond paper showing a fairly constant 
Mullen bursting test. After drying, a series of the painted 
sheets were tested for thickness, bursting strength, and tensile 
strength, with a direct reading spring micrometer, Mullen tester, 
and Scott apparatus, respectively. Duplicate sections about 


* Hiding Power of White Pigments and Paints. 

A. F. Pfund—Jour. Franklin Inst., 1919. The Colorimetry of Nearly 
White Surfaces. 

A. F. Pfund—Jour. Franklin Inst., 1920. An Instrument for Measuring 
the Hiding Power of Paints. 

R. L. Hallett, Proc. A. S. T. M., 1920. A New Colorimeter. 


ee en 


PHYSICAL EXAMINATION 11 


18” square of the coated paper were then lightly fastened at the 
ends to wooden decks, and exposed on the laboratory roof, facing 
south, at an angle of 45 degrees to the vertical. At the end of 
two months, the spetimens 
were retested. The results 
are recorded in the charts. 
When first approaching the 
problem, it was thought ad- 
visable, if possible, to devise 
an apparatus that would ap- 
ply a coating of uniform 
thickness of any kind of 
paint product to be tested. 
Much experimental work was 
carried out, and several mar- 
keted gummed-paper wrap- 
ping tape machines were ex- 
perimented with. The re- 
sults, however, due to difficul- 
ties in exerting uniform ten- 
sion upon the rolled paper, 
were not encouraging. Ap- 
paratus with steel and with 
glass coating blades, similar 
to those used in the mechan- 
ical coating of oilcloth with 
white enamel, was also con- 
structed and experimented 
with, but ultimately found to 
be mechanically deficient. On 
es 5 full size apparatus in oilcloth 
IGURE . 
Testing Paint Film on Paper for Sie SU ss Dae saat coated 
Tensile Strength. with films of practically uni- 
form thickness, but such a 
machine would not be applicable to or available for routine test- 
ing work. Pending the devolpment of a mechanically perfect 
coating machine for laboratory use, the writer resorted to the 
old-fashioned hand-brush method of paint application. It ap- 
pears, as shown by the several measurements in the charts, that 
most films applied by this method do not vary in thickness to 
any marked extent at various sections on one coated sheet. 


12, EXAMINATION OF PAINTS, VARNISHES AND COLORS 


It was noted on the day following the drying of the last coat 
of paint or varnish that the paper sheets coated with interior 
short oil varnish would upon even slight bending, show a large 
number of cracks and checks, while all long oil varnish products 
were very flexible. In fact, much information regarding the 
physical nature of the various coatings was obtainable by han- 
dling the coated sheets. 

When coating the specimens, it was noted that some of the 
liquids, such as raw linseed oil and raw linseed oil paints, 
rapidly penetrate the paper and thus waterproof the back as 
well as the front. Other coatings, such as rapid drying var- 
nishes or heavy bodied oils, showed very much less penetration. 


FIGURE 2 
Samples After Exposure on Paper. 
Top—Long Oil Spar. Top—High Gum. 


Lower—High Gum Rubbing. Lower—A Cellulose Dope. 


PHYSICAL EXAMINATION 13 


From this result it is recognized that the tests may not be 
strictly comparative, as in some instances the films would stand 
out from the paper to a greater extent than in others. On ac- 
count of this condition, it was suggested that the paper to be 
used for further tests be coated with a preparation that would 
be unacted upon by the paint or varnish liquids. Gelatin was 
proposed for this work. Due to its hygroscopicity and its pos- 
sible effect upon film separation, it was found the paper might 


FIGURE 3 
Experimental Coating Arrangement. 


better be treated two or three days before testing, with a uni- 
form coating of boiled oil, which acts as an insulating medium for 
the various types of material under test. The first coating 
waterproofs the back of the paper, and renders it better suited 
for exposure. In some more recent tests the writer has secured 
the bond paper to small frames and then applied the coating to 
be tested. 

In an effort to set a more exact requirement for “bending 
test” than that usually prescribed for varnishes, some of the 
coated papers were tested in the Schopper folding machine, so 
widely used for testing paper. The results were not satisfac- 


14 


Material. 


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EXAMINATION OF PAINTS, VARNISHES AND COLORS 


TaBLE I 
Thickness ) Appearance 
of Coated | Average | Average | Average of Film 
Paper Thick- | Mullen | Tensile After Ex- 
Inches. ness. Test. |Strength.| posure for 
Months. 
.0032 
.0032 .0032 Rough 
.0033 Dirty 
eee te al 30 
Ea eee 28 16 
.0042 Very 
.0038 .0040 Good 
.0040 Rather 
asi bee SR 28 21 Dirty 
Poe Oe 29 2A 
.0046 Very 
.0045 .0046 Good 
.0046 Rather 
Rope Uh 31 23 Dirty 
Se SRA? 32 26 
.0047 
.0046 .0047 Very 
.0048 Good 
SiPKis a nee Biss 20 
3 Marat Gases 37 23 
.0060 
.0055 .0056 Good 
.0055 Rather 
ay ee 34 20 Flat 
Rae, he 32 18 
.0033 
.0034 .0034 Small 
.0035 Shrinkage 
« hkl ME 33 36 Cracks 
5 Se eas 32 33 
.0034 
.0031 .0032 Great 
.0033 Shrinkage 
seb, aoe Aaa 32 18 Cracks 
Bee ee els So 23 15 
.0035 
.0030 .0033 Large 
.0035 Shrinkage 
se ostane 33 af Cracks 
5 CR aa aie 24 15 
.0060 
.0052 .0053 
.0048 Excellent 
es area AR 39 27 
Le ere a 29 27 


PHYSICAL EXAMINATION 15 


TaBLE I—Continued. 


Thickness Appearance 
of Coated | Average| Average! Average of Film 
Material. Paper Thick- | Mullen | Tensile After Ex- 
Inches. ness. Test. | Strength.! posure for 
Months. 
MARINE Spar VARNISH .0060 
.0056 .0056 
.0054 Excellent 
eee Ne ea SS, 46 30 
STATE © ESS ls ee 36 pHi 
RUBBING—POLISHING .0056 
V ARNISH .0057 .0056 Shrinkage 
.0056 Cracks 
Re ee 39 26 
of, (0S SS es 33 vali 
CaBINET RuUBBING VAR- .0062 
NISH .0063 .0063 Shrinkage 
.0065 Cracks 
Uta OS ik all) i i 35 Ze 
UA Ae DA ee se aa ol 24 
MrxIna VARNISH .0050 
.0056 .0053 Cracking 
.0052 and 
APE ON aE Oe ew ie er 36 26 Flaking 
hae ee) UR Se eat ey 30 23 
FLoor VARNISH .0055 
.0055 .0053 Very 
.0050 Good 
Le ee ee ee oe oh ees 35 24 
Ae aye ae es a 31 23 
100% White Lead .0065 
.0072 .0067 Very 
0065 Good 
“oP "SL DG Ae ie a ea 36 34 
AER Reo oh. ke ot 28 
(ef White Lead... .. 2.°.. .0068 
ao “ane Oxide... 2. ..... .0068 .0067 Very 
.0067 Good 
ej Pid A ee eG 36 29 
1) ye 8 Alea i a ee 41 30 
50% White Lead......... .0070 
PM) 7p, ZOMOMXIGES . ee oe .0070 .0068 Very 
0066 Good 
Me eP ee ee pid, ke. 38 34 
LSS ell eae) 44 32 
25% White Lead .0065 
Wor eme Oxide..i....... .0066 .0066 Very 
0066 Good 
Rene ch ec Ve lac ae eet 39 34 
et SL en rr (ere ae 45 32 


16 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


TaBLE I—Continued. 


Thickness Appearance 
of Coated | Average | Average | Average of Film 
Material. Paper Thick- | Mullen | Tensile After Ex- 
Inches. ness. Test. |Strength.| posure for 
Months. 
100% Zine Oxide .0067 
.0065 .0066 Very 
.0066 Good 
JAN. Orr ea ein ele ea 40 36 
Mar Osea se eee eee 45 
ExTerIonR WHITE PAINT 
White Lead 50 .0082 Very 
Zine Oxide:s6sn.0.2 see .0086 .0080 Good 
Ashestane: (ie he eal oe .0073 
Barytes 7 
A Wats RAO eo Phe ai) ORME - CMR S 44 40 
Mar. 0) tie fo CSR hase yee 46 a2 
Guoss WHITE .0069 s 
Lithopone 75 .0070 .0069 _ Very 
Zine Oxide 25 0068 Good 
JUIL- O ciucka adiet os Use ace Tee 42 39 
War Oe os ae Ae ae ee 41 ptf 
INTERIOR WHITE ENAMEL .0059 
No. 1 0061 .0060 : Very 
100% Zine Oxide .0062 Good 
ATES. ok! wosndtacnes ahs by eee 41 34 
Mar.'9 ok. sae eee 43 23 
InteRIOR Fiat WHITE .0063 
100% Lithopone .0068 .0062 
. 0055 Good 
Nh Res CO ae Ae FM ay irs PA 36 28 
Mar 06.00 06h re ee 29 yd 
MaRINE BuLAck .0062 
Spar Varnish 95% .0076 .0065 Very 
Carbon Black 5% .0058 Good 
Ja Oe te ee Eh pee a2 33 High Gloss 
Mat. Oe’ i Bae eee, © 38 29 
Rep Ho.wp ParntT .0063 
Iron Oxide in Thinned .0067 .0066 Good 
Spar Varnish .0068 Rather 
Jat Boe per ee 23 27 Flat 
Mia ts OS ee Gr oko are 29 29 
RED,PAINT .0056 
Iron Oxide in Hydro- .0058 .0058 Good 
carbon Oil .0058 Rather 
TN Coy eis Cae aie Ue OL Oe eater 28 ly Flat 
Wars Geel Sona a aay ee ee 30 23 
p LEAD 0070 
oe 0080 .0077 
0083 Very 
Ee HOI ee RA are IS, Pe BN 40 33 Good 
Mars 0:3 hae ek eee 45 32 


PHYSICAL EXAMINATION Ly 


tory on paper coated on one face. With double coated paper or 
with stripped films this test might afford much information. 

In studying the results of the tests referred to, the reader 
must be cautioned not to place too much emphasis on the differ- 
ences shown by the various types of products. While it is un- 
doubtedly true that certain indications are given by these tests, 
it would probably be better to await the developments of further 
work before accepting them as at all indicative of the results to 
be obtained on actual weathering of the same samples over long 
periods of time on a normal base, such as wood or metal. 


The most comprehensive work conducted on stripped paint 
and varnish films is that of H. A. Nelson. (See Proc. A. S. T. M. 
1921, page 1111.) 


Hiding Power of Films.—Probably the most accurate device 
for determining the hiding power of liquid paints is that devised 
by Dr. Pfund. For full description see page 19. This instru- 
ment has found quite a wide application in the trade. An ap- 
paratus was designed along a somewhat similar principle by the 
present writer, but giving direct readings without manipulations 
of the clear glass cover top. It is free from the possible criticism 
of pigment accumulation at localized spots, due to working back 
and forth of the cover glass. The base of the apparatus (10 cm. 
in length and 24% cm. wide) is of opaque white glass or of opaque 
black glass, according to whether white or colored paints are to 
be tested. At the end of the base is a metal piece made of Ger- 
man silver, permanently cemented on. This metal piece is 1 mm. 
thick. The surface of the glass base is divided into 10 equal 
parts, thus making the readings between each part 1/10 mm. 
A broad horizontal etched line passes down the middle of the 
glass base. The liquid paint to be examined is poured on the 
base, and the clear glass cover plate placed on the apparatus. 
The visibility of the longitudinal line disappears at a point be- 
tween any two of the cross lines, which can be estimated in 
tenths of a division. The thickness of the paint at the point of 
hiding may therefore be directly read off in hundredths of a 
millimeter. Further experiments are being made to improve 
the apparatus. 

For determining the relative hiding power of liquid and also 
dry paint films, the writer has devised a rather simple method 
which uses a sheet of bond paper upon which squares of black, 


18 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


dark gray, light gray, and other graduated tints of gray are 
printed with wood blocks. These are lettered from A to H. 
After the sheets are furnished by the printer, they are kept 
in stock in the laboratory, and a brush coat of any experimental 
paint is applied in comparison with a standard product. While 
possibly subject to criticism from several angles, this method 
has been found satisfactory for general comparative work. 

Other sheets of paper are printed with blocks of red, blue, 
green and yellow. They are then sized and varnished to deter- 
mine durability of the varnish over various colors. 


PAE 


5 


a my ms 


FIGURE 4 


Shaded paper for comparing Color block paper for varnish 
hiding power of paints. liquids. 


CHAPTER II. 


PFUND PAINT TESTING INSTRUMENTS. 


Three valuable instruments for testing paints and pigments 
have been designed by Dr. A. H. Pfund, Associate Professor of 
Physics at Johns Hopkins University. They were originally de- 
scribed in the Journal of The Franklin Institute for N ovember, 
1919, March, 1920, and April, 1921. An abstract of these, as 
prepared by Dr. Pfund, for this book, together with additional 
comments by the present writer and results obtained in this lab- 
oratory, are given below. 

The Pfund Cryptometer.—This is an “absolute” instrument 
by means of which it is possible to determine the hiding power 
of a paint and of a pigment. 

Hiding power may be defined as that property of a paint 
which enabiles it to obliterate beyond recognition any back- 
ground upon which it may be spread. Since the color of the 
background affects the numerical value of the hiding power, a 
black background is chosen for white paints and, conversely, 
a white background for black paints. In the case of colored 
and gray paints, it will be necessary to carry out measurements 
for both types of background. 

The idea underlying the construction of the cryptometer is 
this: granting that an infinitely thick layer of paint will hide a 
given background completely, it is sought to find the least thick- 
ness of paint which will be as effective in hiding as is the in- 
finitely thick layer. 

The form given the instrument is shown in Fig. 5. Here, A 
is a plate of black glass 14 x 5 X .6 em. whose upper surface 
is optically flat. A transverse groove, B, about 2 mm. deep and 
1 cm. wide, is cut in the upper surface and a millimeter scale is 
etched, as shown in the drawing. Resting upon plate A is plate 
C (7 X 3.5 X .6 cm.), whose lower surface is likewise optically 
flat. A strip of thin steel, D; 0.45 mm. thick, is attached to C, 
so that a wedge-shaped layer of white paint may be formed be- 
tween the plates. This wedge terminates abruptly at the “in- 
finitely thick” layer, B, and, so long as the hiding is not com- 
plete, the line of demarcation is visible. By sliding the wedge 
to the left it is finally impossible to see the edge. From a knowl- 


19 


20 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


edge of the angle of the wedge and the reading on the scale, it is 
possible to calculate the thickness of this critical layer lying im- 
mediately above the edge B. Now, in advancing the plate C 
until the line of demarcation can no longer be seen, we have 
overdone it, so to speak. To correct this, we must reverse the 
motion of the wedge until the edge can just be distinguished 
over its entire length. The mean value of the reading corre- 
sponding, respectively, to disappearance and appearance of the 
edge, yields the desired result. Since the fading away and re- 
appearance is so gradual, due to the fact that the least percep- 
tible increment of intensity which the human eye can detect 
is 1 to 2 per cent (Fechner’s Law), it is clear that no high 
degree of precision is attainable by this method. By taking ten 


Diagram of Pfund Cryptometer 


pairs of readings it is found that the average deviation from 
the mean is about 5 per cent. 

The hiding power of a paint may be obtained at once from a 
knowledge of the wedge-constant K (increase in thickness of 
paint film per unit linear advance along etched scale) and of 
l the wedge-reading at complete hiding. Lumping together the 
various numerical constants and recalling that 1 is measured in 
millimeters, it is possible to express the hiding power (H-P) of 
a paint by the simple relation: 

40.7 


H-P = square feet per gallon. 


A sharp distinction must be made between the hiding power 
of a pigment and that of a paint. Not only are these quantities 


PFUND INSTRUMENTS 21 


expressed in different units, but they are not necessarily related 
in the sense that a pigment of great hiding power necessarily 
produces a paint of correspondingly great hiding power. Tak- 
ing up first the hiding power of pigments, let us consider an 
intimate mixture of x grs. of a white pigment and OES a OF 
colorless (or very pale) linseed oil. This mixture is tested in 
the cryptometer and the critical thickness producing complete 
hiding is found. Let 


t=thickness of critical layer (in cms.). 

b=numbers of grs. of pigment in a disc of 1 cm. base and thickness ft. 
Then, if b grs. pigment hide 1 sq. cm., we find the number of sq. 
em. A covered and hidden by 1 gr. of pigment from the relation 


zi 
bes Ts21 2p Aor-—= A; 
b 


Since the hiding power is better the thinner the IAVEr oie 

smaller than b, we may define the hiding power of a pigment as 
the reciprocal of the number of grs. of pigment mixed with 
colorless linseed oil to painting consistency, which are necessary 
to hide a black, non-absorbent area 1 sq. cm. This is numerically 
equal to the number of square centimeters covered and hidden by 
1 gr. of pigment. Hiding powers of pigments will, therefore, 
be expressed in terms of sq. cm. per gr. The mode of calculating 
the hiding power of pigment and paint may, perhaps, best be 
illustrated by means of an actual determination: 


Paint: 
Basic Carbonate White Lead—72% by wt.—Density 6.81 Specific Vol. 0.147 
Linseed Oil —28% by wt.—Density 0.92 Specific Vol. 1.08 


Cryptometer constant K = 0.0078 
Cryptometer reading at complete hiding: 1 = 25. mm. 
120% 47 10.6 
30.3 


28 X 1.08 = 40.9 i Ce paint contain 72 grs. pigment 
2. = 0.567 c.c. contain 1 gr. pigment 
O07 7 OO6'C sr peegiier 
KI. 0.0073 x 25 =31.1 area covered by 1 gr. pigment 


. H-P (pigment) = 31.1 cm’ per gr. 
H-P (paint) = mes = 223 sq. ft. per gal. 

These illustrations will suffice to show how ealculations are 
carried out. A table of hiding powers, determined by this 
method, is presented elsewhere. 

The Pfund Colorimeter for Nearly White Surfaces.—In view 


pA EXAMINATION OF PAINTS, VARNISHES AND COLORS 


of the circumstances that ordinary colorimeters are entirely too 
insensitive and that visual estimates depend upon the character 
of the comparison surface, the present instrument was devised 
to yield quantitative colorimetric data for nearly white surfaces. 

The idea underlying the construction is as follows: If we allow 
white light to fall upon a surface that is faintly greenish, the 
light reflected diffusely will contain a slight excess of green; if 
now this light be allowed to suffer reflection from a second sur- 
face, identical with the first, the light thus twice reflected will 


FIGURE 6 
Diagrammatic Representation of Pfund Colorimeter. 


contain a greater percentage excess of green than before. By al- 
lowing, similarly, a third and a fourth reflection to take place, the 
accentuation of the green tint continues and finally becomes so 
pronounced that it may be measured readily. This is the method 
of “multiple reflections,” according to which only truly non-se- 
lective (white or grey) surfaces leave the character of multiple 
reflected light unmodified. Any outstanding tint, however, is 
accentuated. % 

The apparatus as actually constructed is shown in Fig. 6. 
Here L is a powerful Mazda C lamp which illumines the outer 
portion of the circular disk A, whose upper surface is covered 


PFUND INSTRUMENTS ae 


with the material to be studied. The light, diffusely reflected, 
illuminates the lower (similarly coated) surface of the disk B 
which, in turn, illuminates the central portion of the disk A. The 
light, after multiple reflections, passes upward through a central 
opening in B and is reflected horizontally by means of the pho- 
tometer cube P. Another beam of light leaving L is reflected 
from a disk of clear optical glass G, roughly ground on both 
sides. (Without going into details it may be stated that the most 
painstaking tests have shown that such a plate reflects visible 
radiations non-selectively.) This light passes through the tube T 
and fills the upper half of the field of view of the photometer cube 
which has a horizontal line of demarcation and which is viewed 
through a simple eye-piece yielding a linear magnification of 2.5. 
The intensity of this beam is varied by rotating the disk G about 
a horizontal axis. A pointer, attached to the rod bearing disk 
G, moves over a graduated scale which has been calibrated in 
terms of coefficients of diffuse reflections. The true values of 
such coefficients are first determined for a series of grey pastes 
(zine oxide, glycerine, bone-black) of varying brightness by 
means of an absolute reflectometer. The colorimeter plates are 
then covered with these same pastes and scale-readings at photo- 
metric balance are recorded. : 

As a result of multiple reflections, the difference in scale 
reading corresponding to surfaces of slightly different bright- 
ness is about four times as great as it would have been had but 
a single reflection been used. 

While this colorimeter lends itself admirably to the methods 
of monochromatic colorimetry, it has been found by actual 
experience that useful results are obtained more simply through 
the use of color-screens. Accordingly, color screens of dominant 
hue 480 pp» (blue), 540 nu (green) and 605 pp are successively 
placed in the eye-piece tube at S and photometric balances are 
established. The scale-readings thus obtained are then evaluated 
into reflection coefficients by referring to the calibration curve. 
This is essentially a spectrophotometric procedure. 

The final results are presented in the form of curves where 
abscisse represent wave-lengths of the color-screens and ordi- 
nates, reflection coefficients. A characteristic series of such 
curves applying to modern paint pigments will be presented 
elsewhere. 

Hiding Power and Brightness of Pigments.—The writer se- 


24 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


cured from manufacturers, a series of white pigments represen- 
tative of those produced in commercial quantities at the present 
time, and widely used in the industry. Portions of these pig- 
ments were submitted to Dr. A. H. Pfund who rubbed them up 
with glycerin and made careful measurements of their bright: 
ness, with the following result: 


Taste I]—Brightness of Various Pigments 


Coefficient of Diffuse Re- 
flection (MgO =99.4%) 
No. Pigment Pigment in Glycerin 
Blue Green Red 
A—480uu} A—560 | A—630 
1 | Basic Sulfate—White Lead.............-...- 81.2) 1587, Genes 
oe Basic Carbonate—White Lead............... 79.8 82.7 84.7 
~ 3> | Bleakrolytic White Lead. ss) Aenea eae s6.4 | 88.0 | 89.0 
o£) Old Process: Lithopone }...) Ae ee 84.7 87.2 88.4 
5 | Leaded Zinc (35% Lead Sulfate).............| 78.4 | B20") ) Baem 
ae Modern Process Ged) Lithopene: vay. ee 87.2 87.6 87.8 
Meee Modern Process K. L. Lithopone............. 88.9 88 .2 88.2 
eg Antamonious Oxide: .- anh ek oe 86.4 89.0 90.1 
ris Titanox: (High oi) absorption); 2... se ee ee 83.1 87.2 89.5. 
este Titanox ‘(Low oil-absorption)..o:7o5s a0 + eee 86.8 89.0 90.1 
“42 | Zine Oxide (French process) 4.2. 0 ee 88.2 | 88.9 | 89.5 2 
“43 Zine Oxide (American Process).:....3........ ey pare 86.0 86.8 
ore Modern Process A. Lithopone.............¢.. 88.9 87.8 88.0 | 
Pa Modern Process 8. Lithopone (Regular)....... Sh en 98.7 | 89.7 _ : 
pate Modern Process 8. Lithopone (Special)........ 88.4 $7.8 | 87.4_ 
"| Modern Process G. 8. Lithopone..............| 88.4 | 88.2 | 88.0 
a os Modern Process A. Bk Label Lithopone....... 98-7.) geupos ae 
aed Modern Process A. Bl Label Lithopone........ 88.7 | 88.2, CoCr 


a | | 


PFUND INSTRUMENTS 20 


TaBLE Il]—Hiding Power of Pigment-Oil M ixtures, Hach Containing 50 Per Cent 
Pigment and 50 Per Cent Linseed Oil by Weight 


Paint Pigment Hiding Power 
No. Sq. Ft. per Gal. 
1 Basie Sulphate—Wohite Lead...2..0.o. 2.02. oe... 116 
2 Basic Carbonate—White Lead. ..................... 145 fee 
3 erro lwiiewW LutesLead\. os iy. ec esl. ee Pee s 145 
4 PimerOURPE MI ENO NONE. 6), . os a Miso eva ole enn 8 145 ae ee 
eet sca 2ind O57, Lead Sulphate)... 200 
ge 3 Moder trocess-G. S.Lithopone.. 6... 22 2s cck sc. 200 a 
v Modern. Process:K. 1. Lithopone.........¢.... — Bx Beet 900 
8. Perper ols xaeniare oe ce Stk te IN eet Gat Wee 
Bey ne Titanox (High oil absorption)............ eu See Beta 290 ey, 
td Titanox (Low oil Eeorp aon) MRE Os eek ee tg Lat ae 943 Bye 
12 Mae Cine rench process)... hoo ow P ee 215 gts 
ree Zine Omide CAmiericah process)... 0. i002. ob ee oe 224 
eae: mpapeerue: rocessuA-Tithopone: . oo. ees Avent oo ek 200 


Another series of these pigments was ground in a mill with 
refined linseed oil, on the basis of 50 parts by weight of pig- 
ment to 50 parts by weight of oil. These gave the following 
hiding power results in the writer’s laboratory. See Table III. 


FOOTNOTE: 
Tests with the Pfund cryptometer on a large number of samples of each pigment examined by 
R. L. Hallett gave average general results as follows: 


Hiding Power of White Pigments 


For complete hiding: 

i Sq. em. Sq. ft. Lbs. per | Hid. Pow. | Hid. Pow. Abieae, 

per gram per lb. LOO SG ent. weight volume Power 
RV bere Wea: eke ea 40 19.5 Dal: 100 100 100 
Basic lead sulphate......... 30 14.7 6.8 WE he 85 
MERIEGR Rs lene elk 80 39.0 226 200 128 350 
Zinc oxide(American process) 46 22.4 4.5 116 96 170 
WSU M DONE hi ck ce vee cl 50 24.4 Aol 125 80 200 


26 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


It should be pointed out, however, that pigments of great bril- 
liancy, such as zine oxide and basic sulphate-white lead, may 
show relatively low hiding power in their untinted condition. 
When slightly tinted with colors to match the color of leaded zinc 
or basic carbonate-white lead, they may show as great or even 
greater hiding power than such pigments.* Hiding power and 
brilliancy should, therefore, always be considered tugether. 

A third series was ground, using only sufficient oil to give con- 
sistency for brushing. These were sent to Dr. Pfund who gave 
readings on his cryptometer, as shown in Table IV. 


sso & 


dL D 
fo} 
Lh | 


vai 
ee 


Reflection Coefficient (Brightness) 
tie 
Pee EVE es 


TLL 
ate 


f+) 
ow 
°o 


O Untinted 
© Blacked 
@Blued 


NT 


| 
fo) 
°o 


° 
7 


B G 
Wave-Lengths 


FIGURE 7 


Curves showing the effect of adding Carbon Black and 
Ultramarine Blue to French Process Zine Oxide ground in 
refined Linseed Oil. 


*See J. Franklin Inst., Nov. 1919, p. 679. Also J. A. Calbeck’s paper, 
“An Application of the Pfund Cryptometer,” etc., Proc. Amer. Soc. Test. 
Mater., 1922. 


PFUND INSTRUMENTS 


27 


TABLE I1V—Hiding Power of Pigment-Oil Miztures Containing Different Amounts 


of Oil 
Percentage By Hiding Power 
Weight As 
Wetermimed syn i les Ce or 
Paint Pigment Analysis 
No. — Pigment Paint 
Sq. Cm. per Gr.| Sq. Ft. per Gal. 
Pigment} Oil 
1 Basic Sulphate White 
Hea er aes 2. 69.7 30.3 25 159 
2* | Basic Carbonate White 
eriiene ys 3 70.4 29.6 36 242 
3 Electrolytic White 
LiGROM OES ose. PS mer 28.7 32 212 
4 Old Process Lithopone | 58.4 41.6 59 212 
5 | Leaded Zine (385% Lead 
PI Dietehe fou ns 63.6 36.4 49 252 
6 Modern Process G. 8S. 
TWCOOPONG Seo io. 61.6 38.4 57 202 
7 Modern Process K. L. 
Lithoponé.......... 58.4 41.6 58 232 
8 | Antimonious Oxide...) 64.5 Bb 44 2323 
10 Titanox (High oil ab- 
BOLO) ose... 60.1 39.9 69 293 
11 Titanox (Low oil ab- 
BORDUOI co uk say 66.3 30.7 57 293 
12 | Zinc Oxide, French 
UVES CE 0G oe ee 50.2 49.8 44 142 
13 Zine Oxide, American 
EMSRS ge cai. | 2 46.4 53.6 55 USS 
14 Modern Process A. 
Lithopone......... 59.1 40.9 54 pas 


* Note low luminosity of this sample in Table II which accounts for 
greater hiding power as compared to other lead. 


The Pfund Paint-film Gauge.—This instrument was developed 
for the purpose of measuring the thickness of wet paint-films. 
Essentially, the instrument consists of a spherical, convex sur- 
face which is forced through the paint layer. Since the paint is 
a plastic solid whose “yield value” exceeds the existant capillary 
forces, the volume of paint originally in a circular disc of 


28 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


section ABCKA is forced into the meniscus AEFGBA. If the 
diameter (D) of the circular paint-spot is measured, and if the 
radius of curvature (R) of the convex surface be known, it is 


R 


o)) 
wn 
° 


Rica k 


1 
WN 


| 


= ‘74; one 
: a | 


RP 
Vhepone DB P rote eae, 


Hi 


N 


\ 


( 
(HINT 


NI 


Reflection Coefficient (Brightness) 
@ 


HLT 
eae) a) 


® 
nn 
.e) 


ee ae 
| 


{o) 


550 


Wave-Lengths 
FIGURE 8 


Curves showing the brightness of commercial opaque pig- 
ments ground in glycerine. Degree of whiteness is indicated 
by the approach to a straight horizontal line. 


found that the thickness (t) of the original paint-film is given 
by the relation: 
ae Le 
~ 16R 

The final form given the instrument is shown in Ea rae 
convex lens L whose lower surface has a radius of curvature of 
25 cm. is mounted in a short tube 7, which slides freely in an 
outer tube T:, The compression springs S keep the convex sur- 


t 


PFUND INSTRUMENTS rh 
TD 


face out of contact with the paint-film until pressure is applied to 
the top of 7:. This instrument is simply rested on a painted sur- 
face, and the lens is forced down as far as it will go. Upon 


+S 2% 

>Re ‘ 
43 AAERRBRRH 
EROS GRD Sw 


FIGURE 9 


Pfund Film Gauge. 


Mark Left on Painted Surface 
by Gauge. 

Seale for Measuring Spot on 
Gauge Lens. 


releasing the pressure before removing the gauge, a circular 
spot is left on the gauge as well as on the painted surface. The 
diameter of the spot on the gauge is measured to 0.1 of a milli- 
metre. If the spot is elliptical, the mean of the major and minor 
axes is determined. A series of readings on at least ten spots, 
judiciously distributed over a given area, yields a fair value of 
the average thickness of film. By referring to the table printed 
below, the thickness of the paint-film in mm. and the number of 


30 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


square feet which would be covered by one gallon of paint may 
be evaluated at once. 

A number of experiments were carried out to check the accur- 
acy of the paint-film gauge. In each case a known mass of paint 
was spread uniformly over a definite area of plate-glass, and the 


FIGURE 10 
Pfund Paint Film Gauge 


thickness of film was calculated in the usual manner. Different 
gauges and thickness of layer were used. The results are briefly 
presented in the following table: 


I II III IV 
Film thickness (by calculation).................. 0.0444 mm. 0.0402 0.0644 0.0638 
Film thickness (by paint-film gauge)... 0.0448 0.0390 0.0652 0.0638 


Considering the roughness of the measurements, the agreement — : 


is surprisingly good. Equally satisfactory results were obtained 
on varnish films. The differences between the two sets of 
measurements rarely exceeded 3 per cent. 

For testing the accuracy of this instrument, ideal conditions 
exist when the paint is grainless and the underlying surface is 
smooth, flat and non-porous. Using a zinc-oxide linseed-oil 
paint spread upon plate glass it has been found, as previously 
noted, that the paint-film gauge yields results which are essen- 
tially correct. However, if the paint is gritty or if the surface 
to be painted is rough, the paint-film gauge will yield film thick- 
nesses which are too small. Conversely, if the sub-surface is 


PFUND INSTRUMENTS ol 


TABLE V 


d = Diameter of paint spot on lens (in mm.). 
t = Thickness of paint film (in mm.). 
t 


d 
In mm. Thickness in mm. Sq. ft. per gal. 

hse, RS Se ee LN Vas eco ORE Wee eee ee oS 18,088 

LS GENO no Seta eae Re apogee 10,175 

nos eS te Sle OT SedS a Sec «ee ey 6,512 

tS Se, ae CHO Out ae) doe Moet tayo 4,522 

ARES SS ee a SAV A AITE emg ss Cao led OR el RBZ 

Pee yet mer fre UGG. A cose Oe aR Re ae eae 2,543 

UES [DAO selene PAD VSS 0, aR 9 ON alr NN le 2,009 
LN, Sesh OM Gat ree eee ae OZ kate Sek tetas, 1,628 
\ he Dee a Se ee ee Weel Nes Ob ee RO ane ea 1,845 
ree ae OB DOOM et iat We ER ors 1,130 
LEG OS ie ee ae a Oa ade gt ans a 963 
1 ee ais eee OA 90 Oia Arnaut Birt foe 830 
1 EO AT Oe sede ae Sas GAD cme east nese ete 723 
RO ee co ek ca” i... OG LO Osi eee cal of aion, 20s, 636 
LESS ORE aoe 2 WTC Biogas Oe gas nie oc 563 
TPO Giants) Cee eae OST opie nie hes eed 502 
ED eo ae WS NGWA SPAR 3 oS Or See Mo 450 
CAL is ae bOOOG Aico pee Par eos 407 
ZBL SEN Rie agen aa CALA). Se hes Aetna a eee a 369 
TS et OE OSes ae "Sot STE Bae Bie eae OOP aa 336 
AA SOD, AN) te to Se sc. Su pe 307 
2B Ae Vee eee Li PARUS lgeee ot ie aeenie ele an 282 
AES Oe aera RS Le 2 Sh oleae ie ae ae eee ER 260 
Ee oa eke | SR LUIE Ts NON Gee On a Rt 241 
ele GIA Rs Ota ae By eae ee en ey EN ech VRS 
DAGSE EAT eae ae TO COO Ss eee 207 
CEs ke ZEOZOs Sa ee ee es 4 193 
rag Lito} 7 Se eal et ae PEO Seek Say eee psn 180 
Lat Gee ee rr Oe £5 aie Ws dee 158 
Uh | UR eee BOO ee cigar oe, Aen 141 
Bi ete eet oe Oe EU cate corte ee es Rane 125 
Bere pee See BG LOO Se ep res CO i ot | ie 3: 


soft and yields under the pressure of the convex surface, the 
evaluated film thickness will come out too large. 

Undoubtedly this instrument will be of great service to the 
paint experimenter in working on the physical properties of 
pigments.* Probably its most important application will be for 
gauging the thickness of coatings applied by the spray gun. 
Sprayed films are apt to be very thick unless the application is 
properly controlled. (See Table VI.) 

The instrument is apparently accurate to within 25% of the 
correct value when applied to fairly smooth planes. This result 


* Readings on glass made with the Pfund gauge by P. R. Croll, New 
Jersey Zinc Co. Research Laboratories as referred to are 1047, 996, 979, 870 
-and 930 or an average of 964 as against a true spreading rate of 1009 
Square feet as determined by weight of paint (error 3.5 per cent.) 


32 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


was arrived at by the present writert after several hundred 
tests upon a large number of paints applied to different kinds 
of surfaces. It should, therefore, be of interest to painters. 


TABLE VI—Measurements with Pfund Gauge on Surface Coated with a 
Spray Gun and Hand Brush 


Tests on Wood. Tests on Metal. 
Spreading Spreading 
Rate, Rate, 
Sq. Ft. per Sq. Ft. per 
Gallon. Gallon. 5 
Mill White Primer: 
Hard Brushlot 2 ee bee eee 868 1093 
SL Gaie oe R rinate eet dey Sae SOE FIP é 607 420 
Mill White Flat: 
Hand )Brushs: er 2 anes 1192 1107 
SDIAY Oe ce eo eee ae 382 557 
Mill White Gloss: | 
Hand: Brust 2 base eee : 1175 980 
SDPO se dela ek ee ie eS AQT 352 


NoTEe: Sprayed films were quite thick and had excellent hiding prop- 
erties. Hand-brushed films were thin and more transparent. 


Some of the factors which make the instrument not wholly 
reliable for measuring the thickness of films on exteriors are 
roughness of wood surfaces, rust spots on metal, slight splinters 
or grain effects on wood, coarse particles in paints that are not 
well ground, and yielding of surfaces under the pressure ap- 
plied to the instrument. 

A series of tests was also made to determine the actual ratio 
between spreading rate as calculated by determining the weight 
of a paint and the number of pounds or gallons applied to a sur- 
face, and the spreading rate as determined by the Pfund instru- 
ment. The measurements of the Pfund instrument were made 
upon the surfaces directly after the application of the paint. 
In these tests dressed lumber that had been primed, and per- 
fectly clean black iron were used. Representative results are 
given herewith: 


Wood.. 
Spreading rate estimated from weight of paint applied........................ 815 
Spreading rate by Pfund gauge... 1175 
Metal. 
Spreading rate estimated from weight of paint applied 2.435 eae 827 
Spreading rate by Pfund gauge... cic.) 1037 


7+ See Circular 132 of the Scientific Section. 


PFUND INSTRUMENTS 33 
a ——————————— 8 


| In another series of tests the following results were obtained: 


TABLE VII 
eet 


Hand Brushed. 


Actual spread- 
Sprayed. arene ing Rate Esti- 
Gauge Test. Gauge Test. mated from 
Weight of 
Paint Applied. 
Mill White Primer: 
Glas eee ot 1088 LEGO senmak teas Pog Ye 
saat 23 aoe eae 925 1001 1073 
WWOOCme astute hos 670 755 885 
Gloss White: 
GCieg ee. 1370 TOS BOM Ca: ie ia cas, Bt 
EE OT My a cg! 925 1052 1017 
NWOOGwes pee 2: 510 686 868 


Ra a a 


In the above tests at least ten measurements were made with 
the Pfund instrument on each test, and the average figure used 
in calculating the thickness of the films. It is of interest to 
note the rather uniform results obtainable in hand-brush appli- 
cation, as shown by the measurements below. 


TABLE VIII—Diameter of Spot in Centimeters 
ieee re a Ye 
Paint No. 1. | Paint No. 2. | Paint No. 3. Paint No. 4. 


1.25 neat 1.45 1.30 

1.30 87 1.45 1.25 

1.10 .90 1.45 1.22 

1.12 .90 1.40 1.22 

1.05 90 1.45 1,20 
eee ee ee a a ee 


Apparently from the above results, the gauge may either 
Overestimate or underestimate the amount of paint applied. It 
is believed, however, that the instrument will be found of con- 
siderable use in painting work. 


CHAPTER III. 


A STUDY OF 
COLOR SYSTEMS, COLORIMETERS 
AND SPECTROPHOTOMETERS 
WITH NOTES ON THEIR POSSIBLE APPLICATION 


IN THE PAINT INDUSTRY* 


Paint manufacturers have often felt the need of defining and 
preserving standards of color. The methods in use at the pres- 
ent time are unsatisfactory. The most widely used method of 
preserving standards of color is by means of painted color chips, 
which may exhibit a slight change over a short period of time, 
depending largely upon the conditions under which they are 
stored. The same difficulty is occasionally met in the case of 
tinned standards either ground as a paint or ground in light- 
colored paraffin oil or in glycerin. It has been realized for some 
time that instruments were being made available by means of 
which a color could be recorded and the results kept for further 
reference. The majority of these instruments, however, have 
been difficult to operate and have involved considerable calcula- 
tions. Consequently little study has been given to them in con- 
nection with their possible use in the paint trade. 

In this paper an attempt has been made to describe, classify, 
and comment upon the various systems of color nomenclature 
and to indicate the usefulness and limitations of various colori- 
meters and spectrophotometers. That some of these instruments 
will soon come into wide usage in the paint industry is believed 
probable. Some enthusiasts even believe that the curve obtained 
by reading a color upon such instruments may be made the basis 
of purchase where exact standards are required. 

The descriptions and comments which follow are based, 
wherever possible, upon actual examination or operation of the 
method or the instrument. When this was not possible, the 
available literature on the subject was searched for the neces- 


sary information. References to original papers treating the ~ 


subject in much greater detail than was possible here have been 


* Abstracted from Scientific Section Circular No. 191, in which many 
color chip and readings are shown that could not be included in this chapter. 


34 


COLOR SYSTEMS 390 
a ————————— 8 


given throughout the paper. A list of some of the more widely 
known books on the Subject of color in general will be found 
in Circular 191 of the Scientific Section. 

Color as one perceives it in an object is simply a physiological 
or optical sensation. We say, for instance, that lamp-black is 
black, and the sensation produced is due to the fact that the 
physical structure of the pigment causes the absorption of nearly 
all visible light rays that fall upon it. When these same light 
rays fall upon zine oxide, they are practically all reflected and 
we say that this pigment is white. Similarly we have the sen- 
sation of red from a pigment absorbing: all rays except those 
that give a sensation of red, while from a green pigment we 
have reflected only those rays that give the sensation of the par- 
ticular hue of green that appears. How simple would be the 
preparation of all colors if we could so change by a simple pro- 
cess the physical structure of some element like carbon so that 
it would reflect red, green or blue in such proportions as to give 
the hue we desired. 


COLOR SYSTEMS OR CHARTS 


Numerous attempts have been made to display on color charts 
or cards large numbers of colors arranged in a definite order. 
These color charts or color atlases, as they are sometimes called, 
have a wide use where an approximate match is all that is re- 
quired. The almost infinite number of colors has made it nearly 
an impossible task to make a series of color chips on which may 
be found any desired color. The intention is not, however, to 
show every desired color, but to give a large number of colors, 
all bearing a relationship to each other and in the form of a 
progression, so that if a Sample cannot be matched on the chart 
it can be stated ‘as lying between two adjacent colors in the sys- 
tem. Most of these color charts contain in the neighborhood of 
1,000 colors, 

The authors of these systems have accepted certain theories of 
color arrangement and have made definite rules which have been 
followed throughout the charts. Following is a brief description 
and discussion of several of the more widely known of these sys- 
tems which the writers have studied. 

Many of the charts described are very difficult to obtain and 
quite expensive. All of them, with one exception (Chevreul’s), 
may be seen at the Library of Congress in Washington. 


36 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


COLORIMETERS 


Numerous types of colorimeters have been devised for the 
measurement of color with optical aid. Colorimeters define the 
sensation which the color produces on the eye and see only that 
which the eye sees—that is, when two sample colors appear the 
same under one illumination they will appear to be the same 
in the colorimeter. But if these same two samples should ap- 
pear to be different under another illumination then they will 
appear to be different to the colorimeter, if the latter illumina- 
tion is used. In other words, the fact that they appear alike to 
the colorimeter is not conclusive proof that they will appear 


alike under all conditions. Two colors may match exactly in 


the instrument under white light and yet be entirely different 
under common electric-light illumination. 

Colorimeters have the advantage that results may be rapidly 
obtained by their use. A measurement consists solely of setting 
three or four calibrated adjustments. In order to reproduce the 
color found at any future time, it is only necessary to set the 
instrument in the same manner as before. In other words, if a 
standard color be measured on the instrument, the same setting 
can be made at a future time and samples compared with this 
setting, thus providing an unchanging reference standard. 

Results agreeing very closely (within the range of the instru- 
ment) may be obtained by persons having normal vision, but 
since the operation of colorimeters depends entirely upon the 
judgment of a match by a particular observer, color blind or 
even partially color blind persons are unable to take readings. 

Colorimeters may be subdivided under two headings. The 
monochromatic type, of which the Nutting Colorimeter is an 
example, and the trichromatic, of which the Jones, Ives, Baw- 
tree, Lovibond, etc., are examples. 

The Monochromatic Colorimeter.—Defines the color under 
examination in terms of dominant hue and per cent of white 
light. Dominant hue is given in terms of wave length. The 


visible spectrum may be divided in a number of parts from 


wave length 440 to wave length 700. The dominant hue of a 
color is the wave length of the spectrum color which most nearly 
approaches the sample under examination. 

The Trichromatic Colorimeter.—Defines a color in terms of 
three arbitrary primaries, Red, Green, and Blue. These pri- 


3 
1 
. 
{ 
he 
x. 
j 
‘ 
4 
4 
5 


COLOR SYSTEMS ST. 


maries vary with the different types of instruments. The colors 
are provided by dyed gelatine wedges, transparent glass filters, 
etc. This class may be further subdivided into two main types: 

those which operate on the Additive Principle and those which 
operate on the Subtractive Principle. 

Additive Principle——Three arbitrary primaries are taken, 
Red, Green, and Blue, with a device for varying the intensity of 
each. The color of the sample is reproduced by varying these 
intensities. 

Subtractive Principle—The light passes through variable 
color filters, subtracting a greater or less amount of a particular 
color. It is not possible to introduce variations of hue by chang- 
ing the aperture as in additive instruments. This variation in 
hue is obtained by changing the thickness of colored filters. 

When a trichromatic colorimeter is employed for analysis or 
synthesis, the color sensation in terms of true red, true green, 
and true blue components depends entirely upon an accurate 
knowledge of the sensation values of the three filters used in the 
instrument. When these sensation values are known, the re- 
sults obtained by the instrument may be transposed by calcula- 
tion into true value. Further, when these true values are known, 
it is then possible to determine by another series of Silonban te 
the hue, saturation, and brilliance of a sample. 

The Eastman Universal Colorimeter* was designed recently by 
Mr. Loyd A. Jones, of the Eastman Kodak Co. During the World 
War it was used to a large extent in determining the color of 
the horizon and of the sea under various conditions. These re- 
sults were then used in the tinting and shading of camouflage 
paints to be used on vessels, ete. 

The instrument has numerous attachments, each for a par- 
ticular use, such as the measurement of the color of liquids, dyed 
gelatines and glasses, another for reflecting surfaces, another for 
light-colored liquids, ete. 

“The colorimeter} operates on the subtractive principle, and 
any desired color is obtained in the comparison field by the sub- 
traction of certain parts from the white light used for the illumi- 
nation of the comparison field. This subtraction is accomplished 
by the use of dyed gelatine wedges. These wedges are made by 


* Jour. Optical Soc. Am., 4:420 (1920). 
+ Quoted from instructions for operating the Eastman Universal Color- 
imeter. 


38 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


coating glass plates with dyed gelatine, so that the thickness of 
the gelatine layer varies from zero at one end to a maximum at 
the other. The three color additive primaries are red, green, and 
blue, and when light of these three colors is combined white light 
is obtained. By using three wedges, each of which absorbs one 
of the three additive primaries, any desired amount of each pri- 
mary may be subtracted from the white light. 

The method of obtaining any desired color by the subtractive 
method may be explained by reference to Fig. 13, The three 


FIGURE 11 


The Eastman Universal Colorimeter. 


squares in the top line of the diagram represent red, green, and 
blue components of white light. Now, if by some means the blue 
component is absorbed, we have left the red and green compon- 
ents which yieid yellow. That is, if the blue component be re- 
moved from white light the remaining light will appear yellow, 
or, in the terminology of the subtractive method, minus blue. 
Likewise, as indicated in the third line of the diagram, if green 
is absorbed, the blue and red components remain, giving magenta 
or minus green. While if the red component be absorbed, as in- 
dicated in the fourth line of the diagram, the blue and green com- 
ponents remain, giving a blue green or minus red. This illus- 


ee a a 


COLOR SYSTEMS 39 


trates the nature of the three color subtractive primaries, name- 
ly, minus blue, minus green, and minus red. 


Blue Green Red 
(Removed) Green Red (— Blue) Yellow 
Blue (Removed) Red (— Green) Magenta 
Blue Green (Removed) |(— Red) Blue-Green 
ee eT hom i 


The action of the (— Blue) wedge in the colorimeter is, there- 
fore, illustrated by the second line of the diagram in Fig. 12. 
When this wedge is set at zero, that is, completely withdrawn 
from the path of light illuminating the comparison field, no ab- 
sortion takes place, but as it is introduced into the path of the 
light, blue lighti is subtracted, from the white light to a greater 
and greater extent as the thickness of the gelatine coating in- 
creases. When this wedge is introduced so that the point of 
maximum thickness is in the path of the white light, a condition 
similar to that indicated in the second line of the diagram exists, 
and practically all of the blue light present in the white light of 
the comparison field is absorbed, leaving the comparison field 
illuminated by (— Blue) or yellow light. The conditions exist- 
ing when the (— Green) and (— Red) wedges are inserted are 
shown in the third and fourth lines of the diagram. 


a Ne 


Blue Removed Green Removed Red 
Blue Green Removed Red Removed 
Blue Removed Green Red Removed 
FIGURE 13 


It is evident that (Fig. 13) if the (— Blue) and (— Green) be 
inserted simultaneously, the transmitted light will be red, while 
if the (— Green) and (— Red) are used together, blue will be 
obtained, and as a third combination if the (— Blue) and 
(— Red) be used together green light only will be transmitted.” 

The readings which are given in the tables and from which 
the curves are drawn are reported in terms of —Green, —Blue, 


40 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


and —Red. It will be seen that if the sample is Green, no green 
should be subtracted, therefore the —Green wedge should re- 
main in the zero position and the reading in this column will be 
zero. When the sample is blue, the —Blue wedge is placed at 
zero and the reading is zero, and when the sample is red the 
—Red wedge is at zero and the reading is zero. In the case of 
colors which do not come under the heading of red, green or 
blue, one of the three wedges must remain at zero, which is de- 
termined by one of the component colors which go to make up 
the color of the sample. For example, in the case of some brown 
samples the —Red wedge remains at zero and the reading in 
the —Red column is zero. 

The readings in the column marked Neutral represent the 
amount of neutral gray which it is necessary to add to match 
the intensity of the sample. 

The operation of the colorimeter is sinnie 

The electric current furnished by a 3 cell 100 ampere-hour 
storage battery is first properly adjusted, giving the correct 
illumination, which is obtained by checking against a standard 
illumination furnished with the machine. After the lamps have 
been lighted, the field presented to the eye is a circle divided in 
half by a horizontal line. The lower half of the field represents 
the color reflected from the sample and the upper half is the 
color produced by introducing the various wedges. In order to 
take a reading, it is necessary to introduce the two color wedges — 
decided upon, until a color match is obtained in the upper and — 
lower halves of the circle. The intensity is controlled mean- 
while with the neutral wedge. When a good match has been 
obtained both in color and intensity, the position of all the 
wedges is recorded. Several readings are made and an average 
taken, as sufficient accuracy cannot be obtained with one setting. 


SPECTROPHOTOMETERS 


A spectrophotometer is an instrument by means of which a 
colored sample may be compared with a block of Magnesium 
Carbonate, which is assumed as the standard white. The spec- — 
tral reflection curve is plotted from the results, which are given — 
in percentage brilliance for all wave lengths throughout the — 
visible spectrum. | 

Previously in this chapter the statement was made that colori- — 
meters define the sensation produced on the eye by a color. A@ 


COLOR SYSTEMS 4] 


spectrophotometer defines the stimulus which incites that sen- 
sation. If we take a color, which to our eyes gives the sensation 
of red, the colorimeter will define the red which we see and 
nothing more. However, if we take this same red and examine 
it with a spectrophotometer we will obtain a Series of values, 
representing the various stimuli, which when combined will pro- 
duce the same red sensation as before. It is due to this fact 
that two colors having identical spectrophotometric readings 
will be one and the same under all conditions of illumination. 
Ives* states that “the only unique Specification of a color is by 
means of its spectrophotometric analysis.” 

Ives continues in the same article that “the objections to the 

spectrophotometer for practical color measurements are obvious. 
It is an expensive and delicate instrument. A large number of 
measurements are necessary to specify a single color. The color 
cannot be reproduced for study or comparison by setting the in- 
strument to the measured values. The results, plots of readings 
against wave lengths, mean little except to a specially trained 
expert. On the other hand, there is no ground for believing 
that satisfactory color measurement will ever be done by any- 
thing except high-grade: and hence expensive apparatus or that 
really accurate color specifications can be made simple.” 

Color is producd by the vibration of a ray of light. This 
vibration has been measured and the result has been termed 
the wave length of a color. As this wave length is exceedingly 
small, a very small unit of length must be chosen. The milli- 
micron, my, or one-millionth of a millimeter, has been chosen 
as this unit. This micron, p, sometimes used, is one-thousandth 
of a millimeter. It will be noticed that on the charts of the 
Spectrophotometer readings of the sixteen colors elsewhere in 
this paper that certain wave lengths have been marked Red, 
Orange, Yellow, Green, and Blue. Abney states that the ranges 
of the wave length of certain colors are as follows: 


Colors | Wave lengths in millimicrons 
NEVE RT YELLS econ cccbecerctecccersacccecglereastiens- from 446 to 464 
hag 464 500 
eS ye eo ee 500 513 
I et ak 518 578 
Ce 578 592 
RE ee 592 620 
ha. a Sa Rm i lena nc a a 620 end or about 720 


* Jour. Optical Soc. Am., 5:469 (1921). 


42 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Theoretically a pure spectral color has only one wave length, 
and the above figures represent all the spectral colors which fall 
under the heading of Blue, Green, Yellow, etc. 


The spectrophotometer may be set on any one of these wave 
lengths and the percentage brilliance in comparison with the 
block of Magnesium Carbonate read. <A series of readings at 
various wave lengths are taken and a curve plotted. These 
curves are commonly called spectral reflection curves. 

Mees* states that “the quantitative measurement of color is 


: FIGURE 14 
The Keuffel and Esser Color Analyzer. (Old Model.) 


undertaken by means of an instrument termed the spectrophoto- 
meter, which is essentially a spectroscope with photometric 
attachments. In this instrument any portion of the spectrum 
can, be isolated and divided into two portions having the same 
color 4nd adjacent to one another. Into one of the beams is 
introduced the colored object to be measured, which produced 
an absorption of the spectral region in question. The other 
beam is then darkened by some photometric means until the 
two patches, as seen through the eyepiece of the instrument, ap- | : 
pear of equal intensity. Since the amount of darkening which 
has been introduced photometrically is known and is equal to the 


*Jour. Ind. and Eng. Chem., 13:8, 729. The Measurement of Color. 
C. E. K. Mees. 


COLOR SYSTEMS 43 


amount which has been caused by the absorption of the colored 
object, we can read from the instrument the quantitative value 
of the absorption at any point of the spectrum. ‘his is re- 
peated throughout the spectrum, step by step, and a curve of 
absorption against the wave length of the spectrum is obtained.”’ 


CONCLUSIONS 


Color charts are believed to be of limited value, for several 
reasons. A color-chart system, for instance, may contain many 
shades or tints of one color, such as blue, but might not con- 
tain a blue which would match a color chip selected by an 
individual. Color charts are usually prepared with flat or matte 
Surface chips which are difficult to match with a gloss chip. 
Color-blind operators cannot use a color chart with any degree 
_ of accuracy. The influence of one chip upon another, because 
of the effect of color environment, makes comparison difficult 
when a chip is to be matched with a chart. On the other hand, 
color standards preserved in the form of color chips have always 
proved useful to the paint manufacturer. This is on account of 
the fact that the eye is possibly more accurate for matching 
colors than any instrument as at present developed. Thus, for 
instance, if a definite color (freshly prepared) is submitted to 
a manufacturer on a color chip, the manufacturer will be able 
to match it with greater accuracy than from a specification 
written from colorimetric readings. 


Paint makers might to advantage keep wet standards (sec- 
ondary standards) of colors in oil liquids, and make spectro- 
photometric readings on freshly prepared color chips produced 
therefrom. These colors chips, as well as duplicates painted out 
at a later date, could be checked again on the spectrophotometer 
at the end of six months. Changes taking place in the secondary 
standards could thus be detected. 


Because of the present lack of refinements in colorimeters, 
that would guard against experimental errors of a substantial 
nature, it is the writers’ belief that such instruments will not 
be of enormous value to manufacturers for ordinary work. 
Colorimeters could, however, be of service in the following man- 
ner. Suppose, for instance, that a paint manufacturer produces 
a colored paint or enamel, and that he paints it out and attaches 
it to his color card as one of his standard shades or tints always 


44 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


available to the trade. If he makes a reading on this color chip 
with a colorimeter, such, for instance, as the Eastman or Baw- 
tree, he can record his readings for future use. If several 
months later he thinks some change in his raw materials has 
occasioned differences that give him difficulty in matching every 
batch of the same tint, he can then have recource to his colori- 
metric standards. By setting the instrument to his recorded 
values for the color desired, he will observe his original standard 
color which will guide him in matching up his paint. If sub- 
stantial changes have taken place, he can make such adjustments 
in the formula as are necessary to lead him to the original de- 
sired tint. It was found, however, that black and many dark 
shades are of such low reflective value as to come outside the 
range of a colorimeter. Their use, therefore, is limited. 

Colorimeters might be of further use in the following man- 
ner: For instance, a color is desired in some far-off place, and 
the reading on the color may be 20 Red, 40 Green, 30 Blue. 
Several days’ time might be required to paint out a sample of 
the material, dry it, and then submit it by mail. Telegraphic 
communication, however, could be made, stating that paint of 
the above specification was desired. Within a few minutes’ time 
the reader in another section of the country could set his colori- 
meter to the specification, observe the color desired, and match 
it fairly well. Thus specifications could be transmitted by tele- 
graph and be thoroughly understandable. For military purposes 
such a method would be useful. 

As a result of growing interest in the subject of color defini- 
tion, instrument manufacturers are making rapid progress in 
the development of colorimeters. Instruments of even greater 
accuracy than those now available may possibly appear in the 
near future. It is believed that such instruments would be of 
value in any paint laboratory. 


With the tint photometer used in our work, observable differ- 
ences were recorded between colors that, although very similar, 
could also be differentiated by the naked eye. Readings, how- 
ever, were made only upon one instrument and by one observer, 
and comparisons cannot be drawn as to the relative accuracy 
of two different instruments of the same make when read by 
various observers. For matching old colors, this instrument 
could not be set up with recorded values given in red, blue and 


COLOR SYSTEMS 45 


green, as has been referred to above, with the ordinary type of 
colorimeter. It will be seen, therefore, that its use in this direc- 
tion would be somewhat difficult to apply, whereas, of course, 
three readings could be set individually. For this reason the 
ordinary colorimeter referred to above might prove superior to 
the tint photometer, although this latter type of instrument is 
relatively inexpensive, easy to handle, easier upon the eyes, and 
possibly more accurate. 

Since writing the above and just before going to press with 
this book, the writer has seen a new model of the Ives tint-photo- 
meter that is much superior to the old one. 


If a manufacturer should make a reading on a color chip 
with the spectrophotometer and then desire at a later date to see 
whether any changes had occurred in the chip or in the paint 
made with the formula, this instrument could not, of course, be 
used for reproducing the color. His method would be to submit 
his paint to a reading on this instrument and ascertain whether 
any change had taken place. Two colors giving the same read- 
ing on the spectrophotometer are always exactly alike to the 
eye under all conditions of illumination. It is possible, however, 
that two colors giving different readings on the spectrophoto- 
meter might also give the same appearance to the naked eye, 
such, for instance, as camouflage colors. A rather long time 
is required to make readings on a spectrophotometer and the 
instrument is relatively expensive. Normal color vision is not 
needed to operate it. A specification for a color according to a 
spectral reflection curve could not easily be transmitted by tele- 
graph. If received by mail, one familiar with color work could 
immediately get some idea as to what the color referred to looked 
like, but it would be necessary for him to experiment with several 
different tints and shades of the color before he could match it 
exactly on the spectrophotometer. It is without doubt the most 
accurate instrument for defining a color. In large laboratories 
it is believed that the spectrophotometer would be of great value. 


46 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


CHROME GREEN 


No. 3—C. P. Chrome Green. 
No. 4—1 lb. C. P. Chrome Green, 25 Ibs. White Lead. 
No. 5—1 lb. C. P. Chrome Green, 50 lbs. White Lead. 


BLUE GREEN YELLOW ORANGE RED 


BRILLIANCE 


BAT SSS 
Z| 


440 480 520 560 600 640 680 700 


WAVE-LENGTHS IN MILLIMICRONS 
Our results at the Bureau of Standards. 
—---~Keuffel & Esser results their laboratory 


FIGURE 15 
Upper curve No. 5. Middle curve No. 4 Lower curve No. 3. 
TABLE IX 
No. 3 No. 4 ‘No. 5 
Wave Our K. & E. Our K. & E. Our K. & E. 
length results results results results results results 
440 7.0 2s 225 15.0 21.4 23.9 
460 6.0 4.9 24.5 22.8 31.4 28.6 
480 8.0 5.8 BL.0 29.1 40.1 36.0 
500 10.0 7.9 37.4 35:4 45.0 42.2 
520 12.0 10.1 40.7 38.4 47.0 44.6 
540 10.0 7.9 38.0 35.3 45.0 43.6 
560 8.0 5.9 33.9 S1eh 40.8 38.3 
580 7.0 5.0 30.0 26.7 36.9 35.3 
600 6.0 4.0 25.9 23.9 oL.2 30.8 
620 5.0 3.6 22.7 2ha0) 29.2 28.9 
640 5.0 3.2 20.9 19.0 26.8 26.2 
660 5.0 3.3 18.9 18.4 25.7 26.6 
680 5.0 2.9 18.7 17.8 24.4 24.8 
700 6.0 2.9 20.3 18.4 26 9 24 3 


a. a 


COLOR SYSTEMS AT 
Eastman Universal Colorimeter Hess-Ives Tint Photometer 
-GREEN -BLUE -RED NEUTRAL RED GREEN BLUE 
'‘00 100 
90 90 
80 80 
70 70 
60 60 
50 50 
40 40 
30 30 
20 20 
10 10 
O O 
— Our results — Our results 
----Eastman Kodak Co. results their laboratory 
FIGURE 16 
TABLE X 
TABULATION OF READINGS EASTMAN UNIVERSAL 
COLORIMETER 
No. 3 No. 4 No. 5 
Our Ee K..Co: Our E.K.Co. Our’ E.K.Co. 
results results results results results results 
BE ARTOON) pe eo. 
Set en... 13.9 16.6 4.6 6.4 3.6 el 
eTOCs 35.2 35.1 20.3 18.6 18.4 16.6 
IeUMecoh vet ee. 44.0 45.0 32.0 88.1 32.0 Boal 
HESS-IVES TINT PHOTOMETER 
peewee ce o.8 | 20.0 26.5 
“TAIN AG 4 Giant gs 13.0 40.0 43.5 
Peierie oes Pe 9.5 30.5 37.0 
HeGMNTIOSIty 2.5.2... 11.1 35.3 39.6 
CALCULATIONS FOR POLAR CO-ORDINATE CHART 
it 206° 202° | 215° 209° 220° at Be 
PREETI OTE. het 24.6 25.9 12:5 12.5 11.0 10.9 


CHAPTER IV. 


PLASTICITY AND YIELD VALUE 


WITH A SIMPLE FORM OF FLOWMETER FOR ENAMELS, : 
PAINTS AND SIMILAR PLASTIC MATERIALS 


The fact that pigmented oils or pigmented varnishes are plas- 
tic bodies rather than viscous liquids, has been clearly brought 
out by Bingham and Green.* Paint and varnish manufacturers 
are beginning to appreciate the value of the principles involved. 


FIGURE 17 
Two Views of Flow-Meter. 


Up to the present time, however, no simple and inexpensive 
device has been developed that would indicate mobility on a 
numerical basis and in a relatively short period of time. It is 


believed that the apparatus described herein will be useful for 


this purpose although the writer has no data to indicate 


* Proc.) A,S. TM Ad, 11641211919); 
48 


5 a ee 


PLASTICITY AND YIELD 49 


whether the results obtained are comparable with those that 
might be obtained on a plastometer. It is presented, however, 
with the view that further work will indicate a rather wide ap- 
plication. Its design was based on an early attempt by R. D. 
Bonney to measure the flow of certain coatings used in an allied 
industry.* 

This method of testing appealed very much to the writer be- 
cause of its simplicity. A similar apparatus designed by the 
writer for measuring the same properties more accurately is 
shown in Fig. 17. It consists of a heavy piece of plate glass hav- 
ing a series of concentric rings 14 inch apart, etched on one side, 
a brass cylinder for holding the paint, and a frame into which the 
cylinder is fitted so that it can be raised vertically. The frame 
is fitted on two sides with adjusting screws which permit ac- 
curate centering of the cylinder. The instrument is operated by 
inserting the brass cylinder firmly upon the plate, and filling it 


FIGURE 18 
View of Cylinder and Disc. 


level with the coating material to be tested. The cylinder is 
then quickly lifted and the coating material allowed to drain 
out. 

The plate should be carefully leveled before using. When the 
cylinder is raised the material flows out covering a circular area. 
It is essential that the surface be absolutely clean and dry; 
otherwise the area covered by the material will not be circular 
and readings will be inaccurate. In cleaning the plate, the 
writer has proceeded in the following manner: After a test, 
the plate is wiped off with gasoline-soaked rag, then thoroughly 


*Drugs, Oils and Paints, April, 1923. 


50 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


washed with soap and water, and later cleansed with alcohol. A 
mixture of equal volumes of benzol and alcohol was also found 
useful in cleaning the plate. It is then wiped dry with, a soft 
piece of cloth. When thus cleaned, very smooth circles as much 
as seven inches in diameter can be obtained. 

The cylinder may also be used in conjunction with the disc 
shown at C in the figure, for determining the weight of a gallon 
cf paint or other material, where only small quantities are avail- 
able. It is made to contain exactly one cubic inch, hence it is 
only necessary to multiply the weight of a cylinder filled with 
paint by 231 to get the weight per gallon. Approximate specific 
gravities and bulking values of the pigments st in milled 
paints can also be estimated very quickly. 

When the cylinder is raised, the paint levels out very quickly 
at first. Paints of a thick, mushy consistency practically cease 
flowing in from 14, to 14 minute. Other paints continue to flow 
over a much longer period of time. Some of those examined 
were still flowing appreciably after 10 minutes. These differ- 
ences in rate and extent of flow might be explained by reference 
to yield value, which is defined as the resistance to flow due to 
the friction of the pigment particles. The hydrostatic head of 
the material causes the paint to flow, while the yield value op- 
poses flow. High surface tension also tends to decrease flow. The 
effects of both yield value and surface tension probably remain 
constant (during a determination), while the hydrostatic head 
gradually decreases. We thus have the hydrostatic head oppos- 
ing the combined forces of yield value and surface tension. 

The paint continues to flow until the opposing forces are equal, 
that is, until the hydrostatic head has fallen to such a value 


that it no longer exceeds the combined effects of yield value and — 


surface tension. Paints of good flowing properties would there- 
fore have low yield values. Low surface tension would also pro- 
mote flowing. 

A little difficulty was experienced at times in controlling tem- 
perature which, of course, has considerable influence on flow. 
On cold mornings it was necessary to heat the plate and then 
allow it to cool to room temperature before using. With the 
laboratory maintained at 70-75° F., it was possible to check re- 
sults quite closely, usually to 14 ia diameter of flow. The re- 

sults obtained by different operators also checked very well. 


a rr 


PLASTICITY AND YIELD 51 


During the course of the work a large number of determina- 
tions were made. Some of the results are given on pages 54 
and 55. 

Results of tests made on white enamels, prepared outside white 
paints, interior flat whites and pigmented varnishes are shown in 
Table XI. 


he] 
a 
Ls a 
== ial ee ak aS 
| ise) yeliplstie aie hele let nl cpel 
2 Sh Sk nara NA 
3 es oe Bs = 
” 
® 
al eS, 
Oo 
c 
Cc 
= 
me) 
ra 
‘S 
3 
oT) 
—~ 
O 
& 
0 
oO 
waBA 
ePoeerer tr tsts tt | 
> BUSES one 


Time in minutes 


FIGURE 19 
Curves from Results on 
1, Raw Linseed Oil 3, Zine Oxide in Raw Linseed Oil 
2, Spar Varnish 4, Zine Oxide in Spar Varnish 


In Table XII the results of tests on a series of lithopones are 
tabulated. These were of different grades and batches. It will 
be noted that the flow varied to a considerable extent. Repeat 
determinations on these after two days’ standing showed some 
slight differences in flow. Tests after standing for some time 
might show even greater differences. 

Judging by the results shown in the different charts, it ap- 


52 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


pears that the flow of paints is very largely determined by the 
vehicle. Of the liquids tried, the spar varnish and the slightly 
thinned Litho Oil produced the most “flowy” paints, although 
these vehicles were of much greater viscosity than the others. 
Since linseed oil itself shows both a greater initial and final flow 
than either spar varnish or thinned Litho Oil, the great changes 
exhibited following the addition of pigments must be due to 
certain inter-relations between pigment and oil. The differences 
might be ascribed to various causes, such, for example, as sur- 
face tension effects, variations in degree of dispersion, with 
resulting differences in yield value, etc. 

There does not appear to be any very marked differences 


between the type of flow of different pigments in the same oil 


or varnish. For instance, all the spar varnish paints (except 
those which liver) continue to flow for a considerable length of 
time, usually more than ten minutes, while the linseed oil paints 
in general show but very little flow after the first quarter 
minute. There may, however, be some difference in the extent 
of flow of different pigments in the same vehicle, but this is 
not conclusively shown by the results described. Had the differ- 


ent pigments been used in each oil on a standard volume basis, © 


much more reliable information might have been gained on this 
point. Table XII, however, indicates that there may even be 
differences between different samples of the same pigment in a 
given oil. 

The above results indicate why an exterior paint may some- 
times “run” and “sag.” For instance, if a pigment in linseed 
oil is applied to a vertical surface, it may look very smooth and 
in place at first, because of its yield value or resistance to flow. 
As the oil starts to oxidize, the yield value immediately de- 
creases because of the oxidized oil formed. The paint may 
then start to flow out and in time may “sag” and present a 
streaked appearance. 

The rates of flow of turpentine and mineral spirits solutions 
of rosin were measured. Results are given in Table XIII. Such 
solutions probably have no yield value, the rate of flow being 
determined by their viscosity and the rate of evaporation of the 
solvent. A few tests made on varnishes indicate that their rate 
of flow may to some extent be proportional to the same factors. 
Some varnishes, however, may actually show slight yield values 


: 
: 
j 


if the polymerized particles of oil and gum are in an emulsoid — 


form. 4 


PLASTICITY AND YIELD 53 
SS —— 


In a most interesting article entitled “Some Factors which 
Affect the Plasticity of a Paint,’* E. C. Bingham and A. G. 
Yates describe the results obtained in grinding certain pigments 
in various proportions in oil for different periods of time in a 
ball mill. The measurements for yield value and mobility were 
made on a plastometer. Rather startling results were obtained, 
many of which explain some of the phenomena observed in our 
own work, such as the yield value being independent of the effect 
of the fluidity of the oil; the mobility of certain mixtures being 
but little affected by the size of pigment particles, ete. Some of 


the important conclusions made by Bingham and Yates are as 
follows: 


1—As the grinding ,of a pigment in oil progresses, the yield 
value at first decreases, but after 30 hours becomes constant. The 
mobility under the same conditions at first increases, passes 
through a maximum, and then decreases more and more rapidly. 
The maximum occurs after about 30 hours in these experiments. 

3—Silica and lithopone have very different plasticity at the 
same weight concentration. When ‘they are compared at equival- 
ent volume percentages, however, the mobilities are nearly the 
same and the yield values are not very different. This fact is 
the more striking since the particle size in the two pigments is so 
different. 

4—Comparing blown oil with acid-refined linseed oil at the 
same concentration of pigment, the effect of the fluidity of the 
medium is shown. The mobility falls off in presumably the same 
ratio as the fluidities of the oil, but the yield value is independent 
of the fluidity of the oil. 

5—Polar colloids—as, for example, aluminum stearate—have 
very slight influence on the mobility, but they have an extraordi- 
nary effect in raising the yield value. 

7—Moisture exerts a prodigious effect on the plasticity of 
paint, 0.5 per cent of moisture raising the yield value from 90 to 
3450, and at the same time reducing the mobility to one-fourth 
of its former value. 

8—Ovxidation and polymerization affect the fluidity of an oil, 
so we should expect the mobility to be affected. It was thought 
that the fall in the mobility on long grinding. might be attribut- 
able to one of these causes, but grinding in an atmosphere of 
mtrogen only prevented it, partially. A paint ground | im an 
atmosphere of carbon dioxide has a yield value three times as 
high as when ground in the air. | 


* J. Ind. & Engr. Chem., Oct., 1923, p. 1033. 


+, 


54 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


The time of the instrument maker and materials for the con- 
struction of the apparatus averaged about $22.00 per set, not 
allowing for patterns. Several sets have been made at this 
laboratory for the industry. 


TABLE XI—Commercial Paints and Enamels—Diameter of Flow im Inches 


White Enamels 


Time in Minutes YY 4 34 1 1% 2 3 4 5 7 10 

No. lossssssss.[ 43 | 49 | 456+| 4%—| 54 | 534+| 5+] 5+] 5'4 | 5Y44| 54+ 
No.2......[4 | 4« | 436+] 4564| 494/44] 5+ | 536-4] 536-4] 54 —| 54 — 
No. 8............| B%+| 356-4| 334+| 3% | 3%+| 8%+| 8%t|4— |4 | 44 | 4m 
No.4............| 894+] 8%—| 44 | 436+| 43+| 496+| 4144+| 4564] 404 | 494-4] 404 
No5....f4 [434 | 46+4| 49—| 40+] 5 | 5¥6+| 5M —| 5M —| 5M 4+] 54— 
No.6............4¢@ [4%-|4% [4% [5 | 5% | 5%—| 5m | 5% | B+] 5%— 


Time in Minutes A \% 34 1 1% 2 3 4 5 7 10 

Not............|3% [3% [38% | 3% | 3%+| 3+| 84+| 84+] 8K%+| 84+] 3% 
No. 2.....1......| 24+] 24+] 234—| 254—| 2364] 2944| 236-4] 296+4| 286+] 296+] 2+ 
No.0... 19 | 19% | 194-4] 1390-4] 1394-4] 19¢-+| 194-4] 1944] 1%4—| 1%—| 16— 
No.4...) 196 [156 | 156-4] 154-4] 1944] 1564] 19¢—| 19¢—| 134—| 194 | 194 
No.5............)2% | 2%+| 2%-+| 2%-+| 2%-+| 2+] 24—| 24—| 24—| 24—| 24— 
No.6.ccc:n/2. [2 (2 | 840) 24 1G 0) Sess eee 


Time in Minutes Y% YY 34 1 1% 2 3 4 5 % 10 


Flat Wall Paint...| 244+] 24% 244+] 25+] 234 234+| 2% | 2%+| 2%+]| 2K%4+| 3 


| | —— | | | | | | 
———<—_ | —_—_—_ 


Flat White (int.)..| 234 234+] 23+) 2% 24+) 24+) 2%+| 24+) 24+) 2K%+| 3- 


Egg Shell White 
Gunterion anuetce 3 38Y%—| 3%+!] 3%4+| 3% 3% 3%+| 34%4+] 3%—-| 3% 334+ 


ee | 


Undercoat (int.)...| 33%+] 344+] 3%+ ea 334+| 3%+)| 334+] 3%+4+]| 3%—-—| 3K-| 3K- 
| 


Pigmented Varnishes 


Pigmented Black 
Varnish. 3). /sis 3% 4% 44+) 444+| 436+] 44+4+| 4% 444+) 494—| 484@—| 44 — 


*Pigmented Black |_| | ]|—_—_ 
Varnish 2.5.4 ws 4144+| 43% Bo BM | 8+) BM eee eee 5% | 6— se 
*Green Baking —_—__|__—_ 
Hnameleinuc css 3+ 3% 3% 35+] 3%+| 3%+| 4%—-| 4%+] 4% 4% iz 


ee ee 


PLASTICITY AND YIELD 55 


TABLE XII—Dry Lithopones Ground in Linseed Oil*—Diameter of Flow 


an Inches 

Time in Minutes Y% % 34 1 1% 2 3 | 4 5 a 10 

MewinGrades 7... 3%+| 3% | 3% | 334+] 344] 34] 3344] 3244] 3144| 336-41 3x64 
No. 2Grade....., 254 | 254+] 254+] 214+] 256+| 256+| 25¢+| 25¢+| 25641 25641 2564 
No. 3 Grade... 23, | 2% | 23% | 2% | 234 | 23g | 234+] 29241 29441 2944] 29¢+ 
Bio itGhadast ee es 8 Se Sealer et lee lok lan 
Noi Grades cos. ea Se 3a) 34a) 3%—| gyalsie—lan ba. 
No. 6 Grade......| 244—| 24 | 2% | 2% | 214 | 21% | 214 | 236 | 21 | au law 
No.7 Grade....... 3%—-|3% |3% |3% |3% | 3% | 3% | 3%+1 3%+| 81% +| BK > 
No. 8 Grade...... 34%4+| 3% | 3% | 3% | 34+] 3%+| 3%+1 3%4+| 3%4-+4| a%4| a%+ 
No. 9 Grade......| 3%—| 3% | 3% | 3% | 336+] 33+) 334+] 336+| 3344] 3344| 3%+ 
No. 10 Grade.....| 33% | 334+] 336+] 33+] 3346+| 3%4+| 33¢+| 334+] 3364| 334+] 396+ 


* All paints were made up in the proportion of 100 grams pigment to 100 grams raw linseed ol.i 
In this proportion some samples yielded products of much heavier body than others. 


TABLE XIII—Rosin Solutions 


Time in Minutes A 4% 34 1 1% 2 3 4 5 C 10 
Rosin and Turpentine.........|434 |54 |5%1+/534+/5%—-|5%—-|5K%—-|5K%+\|6-— (6% [6u%- 


634 lex+|l7+ (73% |73¢—-|8% |85¢ [836 |93% lowe+ 


* Rosin and Mineral Spirits... .|6 


* Goes beyond largest circle (914 inches) on plate in about 84% minutes. Still flowing after. 10 
minutes. 

These solutions were made by dissolving 100 grams of rosin in 100 grams of the liquid. In both 
eases fairly smooth circles were formed out to the limit of flow. Turpentine solution was of much 
higher viscosity. 


Rubbing Varnish* 


No. 1 thinned with Turpentine../37% |4 ewe EN al aR 5% |5% 15% [53% |6% 16% 
No. 2 thinned with 67% Tur- 
tine and 33 % Mineral Spirits. |4 Ao mh a ee De eel cases ee 534 «|6 64% |6% Z 7% 


* Two varnishes used contained sufficient thinners to give about same viscosity. 


CHAPTER V. 


AN EXPERIMENTAL DRYING TIME METER 


There have been disputes among producers and consumers as 
as to the drying time of paints, enamels, oils, and various 


varnish products. Many of these have been due to the fact that — 


the method of determining the dryness of a film (touching every 
hour with the finger) has not been well defined, and especially 


———— —_ Fama 
—o. = —< 2 
= mes 

- —— —_ . 


PPD 


I 
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GZ 


y 
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st 
|Z 
|Z 
"|= 
| IZ 
eal ieee 
nd 
NZ 
Z 
IA 
vo 


WW Caw SSN WN 


FIGURE 20 


Diagram of drying time meter with section of stand for film. Later 
models of drum on clock are supported by a lace effect circle of metal 
rather than with wire. 


I 
We 
SI) 
18, 
vi 
‘ 


to the fact that observations could not be made with regularity 
over the drying period which often occurred late at night. In 
an attempt to overcome these two factors, the writer has ex- 
perimented for several months to develop an automatic drying 
time meter. Several types were designed and constructed before 
one that would give satisfactory results was developed. 

It will be noted in the illustration (Fig. 20) that the apparatus 
consists of an alarm clock device fastened on an upright base. 


56 


ee ee a a 


DRYING TIME METER D7 


Attached to the hour hand of the clock is a very lightly con- 
structed wire wheel covered with a circular drum formed of 
light tin plate or of aluminum. The drum is slotted to receive 
the test piece upon which the coating is applied. This winds 
under the mandrel rod at the top of the drum and is pressed in 
contact at that junction with a sheet of soft, light tissue paper 
of the same width as the test piece. Both of these are auto- 
matically pulled from an adjoining double shelf stand, by the 
action of the clock. Just so long as the coating is wet, it will 
Stain the tissue paper at the point of junction, the paper adher- 
ing quite tenaciously to the tacky film. Just at the point of firm 
setting of the coating, the paper will no longer be stained when 
it comes in contact with the test piece and will not adhere thereto 
during its subsequent journey around the drum. 

The test piece developed for this work after a trial of many 
materials, consists of a roll of celluloid moving picture film 
(waste short ends of undeveloped raw stock) that has been light 
struck but not developed. This material was selected because of 
its opacity (white silver coated surface) upon which, applied, 
clear coatings are quite evident. Because of its great smooth- 
ness of surface, paint and varnish coatings do not penetrate it, 
but dry upon the surface somewhat as they would upon glass. 
Moreover, the solvents usually present in paint and varnish ap- 
parently do not affect the film, and they seem to evaporate in the 
same time as they would from tin or glass. Solvents of the ester 
type, or acetone-containing solvents, such as may be used in 
lacquers, could not be used. Moreover, such film is of a standard 
size and character of finish and is obtainable in practically any 
part of the country at a low cost from moving picture firms. 

After the apparatus is set up, it should be standardized by 
applying a coating of paint or varnish to the film and allowing 
it to run for a period of twelve hours. The clock is set at the 
figure 12, at which’ point the slot for the film will be about 1, 
inch beyond the mandrel rod. The length of film pulled through 
over that period is then measured and plotted off into twelve 
Sections with sub-divisions if desired. Each section will be sub- 
stantially 114 inches in length, representing one hour’s time. 
For an apparatus that has thus been standardized, the supply 
of film to be used therein may then be stamped or printed with 
Such divisions as are desired. 

If the drying time of a product is to be determined, which re- 


58 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


quires a 24-hour drying period, a length of film not exceeding 40 
inches will generally be found sufficient. It is usual to attach the 
film late in the afternoon and to make the reading for drying 
time in the morning, the apparatus running automatically over 
night. If the tissue paper at the mandrel rod is still being 
stained, the test is continued. If no stain is shown, the film and 
tissue are both removed and examined to determine point of 
drying as indicated above. 

In an earlier attempt to construct such an apparatus, one with 
a series of pegs upon a revolving wire wheel, into which the 
slotted moving picture film would be drawn, was designed. 


FIGURE 21 


Electrically Controlled Moist Cabinet With Recording Gauges for 
Drying Painted Panels. 


The pegs were so arranged as to cause an apparatus to drop 
sand upon the drying film every hour. The sand would re- 
main adherent to the soft, sticky film. When the coating had 
become dry, the sand would not adhere and would fall off as the 
film continued its downward journey. A fairly sharp line of de- 
marcation indicating the drying time was obtained. This ap- 
paratus, however, offered certain mechanical difficulties that 
were not overcome. 
Atmospheric conditions such as humidity and temperature 
will have a profound influence on the drying time of any 


DRYING TIME METER a9 


product. The results obtained one day may not, for instance, be 
thoroughly in accord with those shown another day. It is the 
writer’s idea, therefore, that the main application of this appar- 
atus will be for comparative purposes in determining the com- 
parative drying time of two products. This could be done by 
using two sets of the apparatus (one constructed with a double 
drum wide enough to accommodate two films would probably 
cause a Slowing down of the clock). Another method would be 


FIGURE 22 
Ventilated Moist Cabinet for Studying Drying Time of Oils and Varnishes. 


to use two small films of approximately one-half inch width upon 
the present size type of drum and apparatus. Tests have, how- 
ever, been made thus far with two sets of apparatus. A varnish 
or oil having a known drying time is used upon one, and the test 
coating upon the other. When check tests upon the same coat- 
ings applied to glass were run at the same time, the drying time 
of the latter as determined by touching with the finger, corres- 
ponded very closely with the results obtained on the apparatus. 

The writer offers this development to the industry for com- 
ment and suggestions for further development. Complete sets 


60 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


can be constructed at a comparatively low cost ($24.00) by ‘a 
mechanic. For those who cannot arrange to have the apparatus 
made, sets may be ordered from the writer’s laboratory. 

Since this work was completed a far superior instrument to 
determine drying time has been developed by J. A. Sanderson. 
A description of the new instrument, which is also based upon 
the retention by the drying varnish, of sand dropped from a fun- 
nel, will probably appear in the 1925 report of the Varnish 
Committee of the A. S. T. M. 


CHAPTER VI. 


A COLOR CHANGE CABINET 


For Determining the Discoloration of Interior Whites.—The 
simple form of cabinet shown in the illustration was designed 
for use in testing the “yellowing” of interior paints and enamels. 
It is made of galvanized iron with a double walled air Space in 


\ 


LEZ LIS: 


= 
ae 
ae 


\ 


Lots 
LTE 
Mmm NLT HUNT 1H aa Ge ( 
LEAH a ot 


RNS 


ha 


N 
EN 


FIGURE 23 
Dark Chamber. Light Chamber. 
Gardner Color Change Cabinet. 


the center. The sides and tops are provided with air ducts and 
holes for thermometric readings. At the bottom of each 
chamber, a shallow pan containing several sheets of blotting 
‘paper is placed. An ounce and a half of water is added to each 
pan and readily absorbed by the paper. This amount is usually 
sufficient to provide high humidity of the atmosphere in the 
white chamber for a period of 12 hours and in the dark chamber 


61 


62 EXAMINATION. OF PAINTS, VARNISHES AND COLORS 


for 30 hours. The entire inner surface of one chamber is coated 
with flat black and the other chamber with flat white. The 
white chamber is furnished with electrical connections and a 75- 
watt blue Daylo Mazda lamp which simulates ordinary noon day- 
light. A 10-foot length, of insulated wire is provided for plug- 
ging into any convenient electric light socket. When the lamp 
is lighted, the temperature in the white chamber will run from 
48° C. (118° F.) to 56° C. (132° F.), at various points, whereas 
the black chamber will show approximately 28° C. (82° F.). 

Application of Black Cabinet.—A series of metal, wood or 
other types of slats are coated with white paint, dried, and 
then exposed in the black cabinet. The warm, humid atmos- 
phere will quickly develop differences in the colors. In two 
days’ time a loss of reflection of about 6 per cent has been 
noticed in one type of paint, due to yellowing of the oil content. 
Marked differences in such a short period have also been noticed 
in various types of marketed industrial paints and enamels. In 
a longer period much more discernible results may be noticed. 
It is believed that these results may be comparable to what 
would occur to paints in a very much longer time when exposed 
on factory walls. 

The addition of a small amount (5 per cent) of ammonia 


water to the water used in the pan in this cabinet will greatly ac- — | 


celerate the yellowing of the paints. 
Application of White Cabinet.—Paints containing pigments 


that are easily fogged by strong sunlight may, after proper ex- q 


posure to the bombardment of transmitted and reflected light 
rays, be affected to some slight extent in the white cabinet. The 
paints may be applied to panels and exposed in the cabinet, or 
the pigment under examination can be rubbed up with a normal 
quantity of the liquid in which it is to be used in paint. This 
may then be spread upon a panel and dried. Half of the surface 
may then be covered with black paper. Daily examination of 
the panels, until a difference is noted in the covered and un- 
covered portions, will be instructive. Similar tests nay be made 
on organic colors that may be easily affected by light. It should 


be remembered, however, that the light from a Daylo Mazda — 


lamp is exteremely mild as compared to that from an ultra- 
violet arc; the latter giving effects in a few minutes that are not 


obtainable over a long period of time by other means. The white . 


ee re ee ree ee 


COLOR CHANGE CABINET 63 


cabinet described above may, therefore, be of but little use when 
a quick test for fogging is desired. The writer is, however, en- 
deavoring to arrange a cabinet with an extra compartment pro- 
vided with an iron arc rich in ultra-violet rays. 
Corrosion.—Hither cabinet may find some application in de- 
termining the comparative corrosion resistance of meta] panels. 
The temperature and high humidity should give noticeable re- 
sults. Similiarly it may be used for determining the rust-in- 
hibitive properties of pigments. In the latter case the pigment 
is mixed to a thin paste with water and applied to a small area 
on a brightly polished steel surface. After exposure for forty- 
eight hours, the test plates are removed, the pigment washed off, 
and the area formerly covered by the pigment examined for 
Signs of rusting or etching. 
Drying of Paints and Varnishes.—The drying of paints or 
varnishes in moist atmospheres at definite temperatures might 
be determined in either cabinet, under light or dark conditions. 
Other applications of the cabinet may be developed. It is easily 
constructed and can be made by any local tinsmith. Those who 
do not care to have them made locally can secure them from the 
writer at cost. 
Cabinets in which the drying of paints and varnishes may be 
determined under set conditions of temperature and humidity 
have also been designed by the writer. These are shown in 
Figures 21 and 22. They have been described in early publica- 
tions of the Scientific Section. 


CHAPTER VII. 


USE OF THE MICROSCOPE IN EXAMINING DRIED PAINT 
AND VARNISH FILMS 


The microscope has become practically a standard instrument 
in the equipment of paint and varnish laboratories for the ex- 
amination of paint pigments. It is believed that its usefulness 
may be greatly extended by applying it for the examination of 
all finished paints, enamels or varnishes when Spread out and 
dried. The elasticity, hardness, porosity, resistance to water, 
and other physical properties are indicated by examination at 
low magnifications. Some of the illustrations shown herewith, 
which are fully described in the titles, demonstrate this point. 

When new materials are proposed as constituents of existing 
formule, test batches may be made, brushed out, dried and ex- 
amined for the characteristics noted above. | 

Further work has recently been conducted by the writer on 
dried films that have been scratched with a device under stand- 
ard conditions and then examined under a microscope. The 
paper presenting the results is on “hardness” of films and will 
be issued as a Scientific Section circular in February, 1925. 


64 


MICROSCOPE 65 
ee 


FIGURE 24 

Photomicrograph of surface of 
an interior rubbing varnish. Sur- 
face was scratched with a needle. 


Note clean cut effect due to hard 
film. 


FIGURE 25 

Photomicrograph of surface of 
xterior spar varnish. Surface was 
cratched with a needle. Elastic 
ind comparatively soft nature of 
ilm indicated. Also note dark 
pots due to particles of poly- 
nerized oil that have become in- 
Oluble. These particles are often 
he cause of a “sandy” surface. 


FIGURE 26 


Photomicrograph of surface of 
an exterior spar varnish. White, 
Cloudy effect caused by immersion 
in cold water. Water has not 
abraded or injured film but has 
possibly formed an emulsion with 
the outer layer. 


FIGURE } yt 


Photomicrograph of surface of 
an exterior oil coating showing 
effect of boiling water which has 
caused the film to “creep” or pull 
away from the surface, leaving 
crater-like bare spots. To the 
naked eye a white and rough sur- 
face is indicated. 


66 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


FIGURE 28 


Photomicrograph of surface of 
an oil coating that has shown 
peculiar crinkling, probably due to 
surface tension effects. 


Photomicrograph of a drawn 
metal article. Note abraded effect 
of metal. Rapid corrosion would 
follow unless protected with paint 
or varnish. 


FIGURE 30 


Photomicrograph of a _ paint 
coating. Thinner used in the paint 
was too volatile. Upon evapora- 
tion from film, it caused formation 
of small craters. 


FIGURE 31 
_ Photomicrograph of a paint coat- 
ing. Paint was not _ properly 
ground in mill. Note rough, gran- 


ular surface of unground pigment 
particles. 


MICROSCOPE 67 


FIGURE 32 


Photomicrograph of a wall coat- 
ing. Drying in a dusty room 
caused adherence of dust particles. 
These gave surface a darkened 
appearance. 


FIGURE 34 


FIGURE 338 

Photomicrograph of an experi- 
mental flat coating. Paint con- 
tained too much volatile matter. 
Scratch made with a metal point 
shows dry nature of film. 


Photomicrograph of a cross-sec- 
tion of an enamel coating on oil- 
cloth. Note warp and _ filling 
threads of cotton fabric, filled sur- 


face, and 


enamel film. 


smooth outer white 


CHAPTER VIII. 


HARDNESS OF FILMS 


Testing the Hardness of Varnish Films.—A method com- 
municated by William H. Wilkinson, together with some photo- 
micrographs, is given below. Improvements on this method are 
being made at the present time, and it is hoped that some more 
definite recommendation for this very important test will be 
made. 


The two prominent methods for determining the 
hardness of varnishes met with in the literature are 
those of A. P. Laurie, F. G. Baily, and Jahn. The 
method of Laurie and Baily consists in obtaining the 
pressure, applied to a one mm. blunt, hardened steel 
point, necessary to produce a white Scratch on the film, 
when the film is drawn beneath the point. This method 
really measures toughness rather than hardness, since 
the blunt point when placed on an elastic film will have 
little effect up to a certain point due to the yielding | 
nature of the surface over which it is drawn. Jahn’s 
method determines the pressure necessary to be applied 
to a cylinder, on which are fastened two blunt, ring- 
shaped knife edges, to produce track-like impressions 
on the film. This scheme also has the drawback in that 
it measures the toughness, elasticity, and adherence of 
the film to the surface on which it is placed rather 
than hardness. : 

Because of the fact that both of these methods use a 
constant point in varying pressure, it was thought that 
more reliable information could be obtained by keeping 
the pressure more or less constant and varying the 
hardness of the point. Such a method is used in the 
testing of the hardness of minerals with Mohr’s scale. 
The problem, therefore, was to find a series of sub- 
stances of varying hardnesses which would cover a long 
range from a very soft up to a very hard varnish. Just 
such a series of substances is put out by the Dixon 
Crucible Co. in the form of seventeen drawing pencils. 
The pencils were arranged in the order of their hard- 
ness, the softest being numbered one and the hardest 
seventeen. It was decided, after careful] experimenta- 
tion, to use a sharpened chiseled point rather than a 
rounded point in that it gives (1) a more definite end 
point, (2) a more uniform cut. 


— i ee 


68 


: 
f 
” 
4 
q 
& 
iH 


HARDNESS OF FILMS 69 


No. 5—Pencil, heavy pressure. 


No. 6—Pencil, medium pressure. 


No. 6—Pencil, heavy pressure. 


No. 7—Pencil, medium pressure. 


FIGURE 35 
Effect of Pressure on End Point. 


No. 1—Pencil 
No. 2—Pencil. 
FIGURE 36 


Gloss Oil Drying Time, 20 hrs. 


No. 3—Pencil. 
No. 4—Pencil 
FIGURE 37 


Gloss Oil Drying Time, 98 hrs. 


70 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


The varnish films were first produced by flowing the varnish 
on clean glass plates, but recently we have adopted the method 
of P. H. Walker and J. G. Thompson for preparing films of uni- 
form thickness by whirling the varnish on a circular, ground- 
glass plate at 300 r. p. m. for three minutes. 

The method of testing consists in ruling off lines on the varn- 
ish film, using the pencils in sequence with medium pressure 
until the point is reached which will cut the film. It has been 
our experience in the last three years that the pressure, provid- 
ing, of course, it is not too light, has very little effect on the 
end point; that is, a point which is softer than the varnish film 
will not cut it, no matter how heavy the pressure, point wearing 
away instead. This is clearly shown in Figure 35. Not only 
will this method give the comparative hardness of the film, but 
will also give information as to the rate of hardening of the 
film. This may be seen by comparing Figure 36 with Figure 37. 

While this method has been particularly used by us in test- 
ing shipments against a standard of the same material, we can 
See no reason why different varnishes could not be compared if 
run under identical conditions; e. g., temperature, humidity, 
thickness of film, etc. Also the method should be applicable to 
testing the hardness of other films, such as paint, lacquers, etc. 


For later work on Hardness of Varnish Films, see Scientific 
Section circulars on this subject to be issued in February, 1925. 

It is hoped that these circulars will include an article by PrH. 
Walker and L. L. Steele, who have developed a very satisfactory 
apparatus for determining hardness. 


CHAPTER IX. 


ACCELERATED TESTING CABINETS 


Accelerated tests on paint and varnish films, through the use 
of ultra-violet light, artificial rainstorms, and low and high tem- 
peratures, have received much attention during the past three 
years. The importance of securing in three weeks’ time infor- 
mation that might require a year in ordinary roof exposure tests 
can readily be appreciated. Even though the results of such 
accelerated tests may not follow exactly those obtained by ex- 
terior tests, they do, however, guide the investigator in de- 
termining the comparative life of certain coatings. Probably 
the first cabinet built to make tests on panels of fair size and 
to afford means of a real study of the problem was that designed 
by H. A. Nelson,* who has kindly prepared the following highly 
instructive resume of his important work. Other later investi- 
gators have designed types of apparatus along similar lines, 
Mougey? having constructed one consisting of a series of panels 
mounted upon a revolving wheel passing through a tank of 
water. As the panels emerged from the water, they were sub- 
jected to a mercury are. The writer has also seen other sets of 
apparatus at the laboratories of the du Pont Experimental Sta- 
tion, the du Pont Chemical Co., and, the Pittsburgh Plate Glass 
Co., all of which depend upon cycles of ultra-violet light and 
water. Two new types of cabinets are also being constructed by 
the present writer and will be described at a later date. Mr. 
Nelson’s article is presented below. 

Development and Present Status of Accelerated Weathering 
Tests. By H. A. Nelson.—Both manufacturers and consumers of 
paint and varnish products have undoubtedly long felt the need 
of information that might lead to the development of a compre- 
hensive system of accelerated testing for weather resistance. 
Valuable beginnings of experimental work along this line were 
made by Gardnert and by Muckenfuss§. The latter developed an 


* Harley A. Nelson, Chemist in Charge of Paint Section, Research Divi- 
sion, New Jersey Zinc Company. 

+ H. C. Mougey, General Motors Research Laboratory, Dayton, Ohic. 

tH. A. Gardner—Paint Technology and Tests—1911, also Physical Test- 
ing of Paint and Varnish, Circular No. 122, Ed. Bureau, Paint Manufac- 
turers’ Association of U. S. 

§ A. M. Muckenfuss—Preliminary Report upon a Practical Accelerated 
Test for Paints and Varnishes—Journal Industrial and Engineering Chem- 
istry, Vol. 5, No. 7, July, 1918. 


71 


{eA EXAMINATION OF PAINTS, VARNISHES AND COLORS 


exposure scheme which was designed to take advantage of the 
changes in permeability of paint and varnish films, applied on 
fine mesh screen or hardened paper, to moisture as a measure of 
deterioration under artificial exposure conditions. The exposure 
involved light (mercury are and tungsten), moisture (revolving 
spray) and cool weather (outdoor night exposures). 
Unfortunately, no investigator has directly followed up this 
work. Possibly the extensive equipment necessary for accur- 
ately following the changes in permeability has discouraged any 
attempt to make routine application of the method. Unfor- 
tunately, too, the great acceleration possibilities in utilizing a 
high concentration of ultra-violet radiations were not then en- 


Atomizing 
Spray nozzles. 


. f f ) pinches. 


FIGURE 38 


Type of apparatus that has been successfully used in accelerated 
weathering experiments. (Nelson.) 


tirely recognized, so that the real possibilities of the scheme 
probably were not brought out. 

Other, more recent, investigationst were directed toward a 
possible simplification of the application of the idea of acceler- 


tH. A. Nelson—Accelerated Weathering of Paints on Wood and Metal 
Surfaces—Proc. A. S. T. M. Vol. 22, Part II, 1922. E 5K 


ACCELERATED TESTING CABINETS 713 


ated weathering. The ideal would, of course, be artificial ac- 
celerated reproduction on painted wood and metal surfaces of 
the normal failures that are observed under outdoor exposure 
conditions. The first laboratory evidence that this might be pos- 
sible was the fact that an ordinary 100% B. C. W. L.—linseed oil 
paint film could be made to chalk heavily by exposure for about 
13 hours under an ordinary 220-volt mercury arc lamp. The par- 
ticular importance of the radiations from the ultra-violet portion 
of the spectrum (below \ = 3800 A. U.) was then demonstrated 
by the fact that only some loss of gloss could be obtained by ex- 
posing similar films for about 300 hours at a short distance from 
an ordinary glass blue-printing lamp. 

For further experiments, a special vertical quartz burner, 30” 
long, was developed so that panels in large numbers and of appre- 
ciable surface area (6” x 12’) might be used. The type of light 
exposure tank that has been successfully used is illustrated by 
Fig. 38. The general flexibility of the apparatus originally de- 
scribed has since been improved by providing a separate water 
exposure chamber where panels are subjected to the action of a 
revolving water spray. 

Only light and moisture were extensively used in the first ex- 
periments and the following results were obtained with paints 
and varnishes on wood and metal panels: 

(1) Loss of gloss and subsequent chalking were easily repro- 
duced by exposure to ultra-violet radiations in and below the 
region \ = 3600 A. U. 

(2) Loss of gloss and chalking were hastened by periodic 
saturation of the paint film, or by maintaining a saturated at- 
mosphere in the apparatus during the period of ultra-violet ex- 
posure. 

(3) Paints made with pigments which chalk readily upon 
normal outdoor exposure were the ones which chalked readily 
under the ultra-violet light. Those pigments which normally re- 
tard loss of gloss and chalking under outdoor exposure conditions 
were found to act similarly under the accelerated conditions. 

(4) Comparisons made with results from outdoor exposures 
showed a ratio of approximately one day to one month for loss of 
gloss and initial chalking. For this the accelerated exposure 
scheme was 24 hours light-cool-24 hours water spray. This ap- 
proximate ratio was then found to exist for a number of paint 
combinations representing both chalking and non-chalking pig- 


74 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


ments. (It should be noted, however, that low temperature ex- 
posures were not generally included in these experiments, and 
that the conditions of the exposure were what are now known to 
be very severe for producing a chalking failure.) 


Ww While Lead 
30 4-OuU/t Oor 


meee see wes 
ew 
_—— 
o— — 


< 


“=~ e@— — .. — 6 


& 
S 
v 
N 
a Basic Lead\St/fate 
Q © - Ou Fe (oJ) 
eo * -Acce/e. 
3 
U30 | 
x : 
KR 3 
j 


oe eee 


Outdoor Exp (rs) 
Accelerated + (hrs) 
Lighta 64% Water | 24% Prefriga /2% Acceleraled 


ha a eee 


FIGURE 39 


Comparison of gloss depreciation curves on typical single pig- 
ment paints under outdoor and accelerated weathering condi- 
tions. (Nelson.) 


~ 


(5) Chalking once started by exposure to light, was ac- : 
celerated by exposure to low (freezing) temperatures, especi- é 
ally when the film had been previously saturated with moisture. é 


ACCELERATED TESTING CABINETS 15 


(6) Cracking was then reproduced to a limited extent on cer- 
tain paints and varnishes, but only with marked success when 
some variations of temperature were introduced (outdoor ex- 
posures in winter were used). 

The above results went far toward proving the practicability 
of the method, and the experiments were continued after the 
installation of a refrigerating equipment which made low tem: 
peratures available down to about —16° C. 

Effect of Variations in Exposure Cycle-—The possible effec- 
tive variables which could then be introduced with the equip- 
ment at hand were: 

(1) Light and heat (50° C. to 60° C.) at comparatively low 
humidities. (Air taken in at outdoor temperatures.) 

(2) Light and heat with saturated atmospheres. 

(3) Water spray (washing action of rains). 

(4) Low temperatures (down to —16° C.). 

Early in the work it was evident that the ratios between out- 
door and accelerated weathering would vary with the nature of 
the exposure cycle used. That great variations in the rates of 
outdoor deterioration are introduced by climatic differences is 
also common knowledge. Obviously, then, the next important 
step was to begin a study of the relative deteriorating effective- 
ness of each weathering factor (alone and in combinations) as 
it might be used in an accelerated weathering’ cycle. 

A comprehensive series of tests with this object in view was 
made on a group of representative. varnishes, of which the de- 
tailed results can be found in the literature.* It is important 
to note that very great variations are observed in the degree and 
type of deterioration, depending what factors are included in 
the exposure cycle and the frequency of change from one kind 
of exposure to another. Briefly, the following conciusions were 
arrived at as to the apparent relative deteriorating effectiveness 
of the exposure factors. 

(1) Most effective (especially in deadening or reducing the 
distensibility of the film). was a water exposure followed by 
light. 

(2) Second and almost as effective was water exposure fol- 
lowed by refrigeration. This apparently not only helped take 
the elastic life out of the film, but also acted as a factor in re- 


* Nelson and Schmutz—Further Study of Accelerated Weathering— 
Proc. A. o.:1.°M., Vol. 24, 1924; 


76 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


vealing the deterioration brought about under light and water, 
etc. 

(3) Next in effectiveness was light (warm and dry) followed 
by refrigeration. This combination apparently served largely 
as a factor which brought out, or revealed weaknesses in the film 
which might be inherent with the original material or intro- 
duced by other exposures. 

(4) Considerably lower in effectiveness was the action of 
light alone. (This refers to the “deadening” action of light 
after the excess absorbed water has passed off and the film is 
fairly dry. The lower the moisture in the film the slower is the 
action of light.) 

(5) Next was water alone which, in itself, appeared to have a 
deteriorating effect. i 

(6) Continued refrigeration, after the film had attained 
equilibrium at the low temperature, had no appreciable de- 
teriorating effect. 

Exposure cycles involving moisture and light were most ef- 
fective when changes were made frequently. Thus the film was 
practically always in a saturated state and the light did most 
damage. Light-refrigeration cycles brought about cracking most 
quickly with frequent changes, but the final deterioration was 
greatest under longer periods of exposure when the light de- 
terioration became proportionately greater. Water-refrigera- 
tion was most effective with moderately frequent changes. 

Wolff* in his recently reported work on this subject concludes 
that cooling a film below the dew point in moist air and the sub- 
sequent freezing of the moisture in the film, are the most effec- 
tive deteriorating factors. It is very interesting to note that in 
the above classification such a combination is ranked a close 
second in deteriorating effectiveness to water exposure (satur- 
ated film) followed by light. Wolff does not state under what 
conditions exposures to light were made in his tests, but if these 
were made at low atmospheric humidities (on dry films) his 
conclusions can probably be accounted for. 

Comparison With Outdoor Exposure Results.—As previously 
stated in the early experiments, an approximate relation was 
established between outdoor and accelerated weathering results 


*Hans Wolff—Testing of Varnishes and Paints, Particularly for Re- 


sistance to Weather—Farben Zeitung, Vol. 26, pp. 704-705, February 9, 
19238. 


ACCELERATED TESTING CABINETS wht 


with moisture and light as the major factors involved. It was 
also subsequently pointed out that this ratio did not hold when 
the exposure cycle was modified to any appreciable extent (for 
example, by adding low temperatures to the exposure). This 
complicates the problem of establishing an exact ratio and it is 
also possible that on account of variations in weather conditions, 
except when averages are made to cover a considerable number 
of years, the accuracy with which such a ratio can be established 
will never be very close. Neither is it probable that any one 
ratio will be strictly applicable except to the particular sections 
of the country for which it is worked out. That is, the acceler- 
ated cycle will have to be modified to suit the climatic or ex- 
posure conditions that are to be simulated. 

The results in Fig. 39 illustrate how deterioration, as meas- 
ured by loss of gloss and chalking tendencies on outdoor ex- 
posures, compares with an arbitrarily selected accelerated ex- 
posure cycle. Gloss determinations were made with the Inger- 
soll ‘“Glarimeter.” The exposure cycle, indicated along the 
abscissa, was selected to give the same average ratio of light, 
moisture and refrigeration prevailing at Palmerton, Pa., over 
the period of one year. The curves given are plotted on a 1:7 
ratio, which appears to fit quite closely for the paints that were 
put out at this time. (Exposure from March to August, 1924.) 
But experiments show that this 1:7 ratio will not hold if the 
outdoor exposure is begun at another season nor have we any 
reason to expect that it would. Essentially, then, all that these 
curves tell is that the reactions of the films to the sum total of 
the weathering agents (artificial and natural) as used in these 
experiments are very similar, even, with pigments that differ 
so radically in their known properties. But this, in itself, is 
very important as further proof of the practicability of acceler- 
ated weathering. 

The degree of chalking produced by prolonged exposure has 
been observed to follow the results from outdoor exposures. All 
results indicate that quite accurate estimates can be made of the 
final chalking characteristics of a paint; that is, whether heavy 
or light, and whether adhering or easily rubbed or washed off. 

Cracking types of failure are reproduced, but up to the pres- 
ent time no such definite time ratios can be reported for paints. 
There is evidence, however, that these will approximate the ob- 
served time ratios for loss of gloss and chalking. As for ex- 


78 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


ample, the observed ratio for cracking on a set of several var- 
nishes was observed to be between 1:6 and 1:7. It is interesting 
to note that this ratio fits the curves in Fig. 39. Other observa- 
tions have been given ratios of approximately 1:10. One dif- 
ficulty is that failures of this type are so often directly affected 
by slight variations in the application and differences in the 
conditions of the undercoats on several panels, that a very great 
number of observations will have to be made in order to arrive 
at reliable conclusions. 

Sources of Ultra-Violet Energy.—Practically all of the work 
so far reported on accelerated weathering of paint and varnish 
products. has' been done with the mercury arc as a light source. 
Convenience in handling and the important fact that the long 
tubes permit equal exposure over larger areas have undoubtedly 
been the reasons for this. But essentially, there is no reason 
why other sources of ultra-violet energy should not be success- 
fully used. For those who are satisfied to work with smaller 
samples on a moderate scale, the iron or modified carbon arc 
types will undoubtedly prove as satisfactory. 

The mercury arc does have a weakness in the fact that the 
ultra-violet transmission of the quartz tube drops as the burner 
is used. Flynn* reports an interesting way to compensate for 
this. He found it desirable to mellow the burners for about 500 
hours. This was accomplished with a 220-volt burner by start- 
ing it at 160 volts drop in the are proper and increasing the 
voltage drop at the rate of 2 volts for every 100 hours of opera- 
tion for the first 500 hours. After this, he claims, no change is 
necessary during the remaining several thousand hours of the 
life of the burner for dye testing. 

It is not yet definitely known whether the radiate in ake 
ultra-violet have a selective action on linseed oil and other or- 
ganic paint and varnish materials, or if the deteriorating effect 
merely increases directly as the wave lengths of the ultra-violet 
radiations are decreased. Experiments designed to determine 
this are under way and more information on the subject should 
be available shortly. The experience of the dye industry, as 
shown by Harrison+ and Flynnt is that for certain dyes, which 


* Oscar R. Flynn—How the Mercury Are Was Made to Imitat 
—American Dyestuffs Reporter, Vol. XII, pp. 837-43, Nee ae ate one a 
ie kee ho eee Society of Dyers and Colorists, July, 


a en R. Flynn—Am. Dyestuffs Reporter, Vol. XII, pp. 837- 43, Nov. 


ACCELERATED TESTING CABINETS 19 


are faded by reducing reactions, the radiations below about 
X = 2900 A. U. must be filtered out to obtain results comparable 
with sunlight exposures. This is especially true on cotton which, 
Flynn concludes, becomes very actively reducing under the ac- 
tion of radiations much below A = 2900 A. U. Accordingly, for 
such dyes, the arc was tempered by interposing thin sheets of 
crown glass. It is possible that such side-reactions might also 
take place in paint and varnish films, but the indications are 
that under the experimental conditions these are not an import- 
ant factor, if they take place at all. For example, preliminary 
experiments (28 inches from a 220-volt D. C. 30” tube, operated 
at 9 amperes) on paints with a series of special glass filters, 
which cut out the ultra-violet step by step, show that all of the 
gloss reduction curves under the different filters are quite 
similar in form, the main difference being in the rate at which 
the gloss falls off and surface chalking takes place. That is, 
filtering out the shorter wave lengths of ultra-violet light merely 
lowers the rate at which the deteriorating reactions progress. 

It should be noted that the results shown in Fig. 39 are from 
panels exposed without interposing any light filter. Properly 
speaking, however, this light exposure is already partly temp- 
ered, when we consider the distance from the are (28 inches) 
and the fact that the quartz used in the burners is not of the 
highly transparent grade. Possibly this choice of light exposure 
conditions has been a very fortunate one and partially accounts 
for the very gratifying agreement with outdoor exposures. But 
our conclusion must be that we do not yet know just how far we 
can go in accelerating the light exposure and still maintain a 
proper balance with the other factors that must enter into a 
complete accelerated weathering scheme. 

In closing, it will also be worth while to point out that the 
work so far recorded has not taken into account the influence of 
many other important, but less universal, deteriorating factors. 
We may mention, especially, industrial gases in combinations 
with light, moisture, etc. These will, of course, have to be 
studied and assigned to their proper places in the final testing 
scheme. 


80 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Coefficients of Diffuse Reflection for Pigments at Different Wave Lengths 
in the Near Ultra-Violet’ 


Wave Lengths Measured in 


Angstrom Units 2c eiee. oc. 4047 3655 3131 3024 2968 
Basic Carbonate of White Lead 83 78 69 65 62 
Basic ‘Lead! Sulfate. 2.54..2.5: 82 60 58 57 56 
A Cheating yoo. ere eh es 75 68 63 62 64 
TSTHOVONG Mss ee ee eh ee 83 66 2 0 0 
Titanium: Pigment..07 25a 82 24 2 0 0 
Lamp: Black 22.2 es a ok 3.8 4.2 4.2 4.3 4.5 
Iron Oxide (69% Fe20s) «0-2... 6 6 6.5 6.5 6.8 
Chrome <yY ellowe 222.0) es 4 2.5 0 0 0 
Zinc Oxide (lead free)....................... 80 3 0 0 0 


* Data prepared by G. F. A. Stutz. 

* The figures given refer-to the stronger wave lengths in the mercury arc. 
Visible light ends at about , = 3900 to 3800 A. U. The Sun’s spectrum 
ends at about ) = 2900 A. U. Therefore, the ultra-violet represented in 
the Sun’s spectrum covers the region from about 4000 to 2900 A. U. 


CHAPTER X. 


DETERMINING THE SPECIFIC GRAVITY OF PAINT 
PIGMENTS 


There is given below the method developed and standardized 
in the writer’s laboratory for the determination of the specific 
gravity of paint pigments. This method was originally pub- 
lished in Circular No. 104. 

1. Standardization of Pyknometers.—Fill the pyknometers 
with freshly-boiled distilled water and bring to temperature of 
15.6° C. Dry and weigh as outlined in paragraph 6. Clean, 
weigh and dry the pyknometers. Fill them with the kerosene 
to be used and bring to temperature of 15.6° C. Dry and weigh 
in the same manner. Calculate the specific gravity of the kero- 
sene by dividing the weight of water into the weight of kerosene. 

2. Drying—Dry the pigment in an oven, preferably electric, 
at 105° C. for 2 hours. 

3. Weighing.—Weigh a sample of the pigment, by difference, 
in the weighing bottle. For blacks, blues, and lakes of light 
specific gravity, use about 1 gram; for inert crystalline pig- 
ments, about 4 grams; for opaque white pigments, 7 to 10 
grams; for red lead, 15 to 20 grams. Due to the hygroscopic 
nature of some of the pigments it is necessary to use a weighing 
bottle fitted with a cork stopper. 

4. Transferring to Pyknometer.—Pour sufficient kerosene 
into the pyknometer to form a quarter of an inch layer in the 
bottom and add a quantity of pigment from the weighing bottle 
reaching approximately three-quarters of the distance to the 
kerosene level. The kerosene should always cover the pigment. 
Stir the sample with a polished round bottom glass rod until 
completely covered by the kerosene, if necessary adding more 
kerosene from the wash bottle. Wash rod with kerosene. 

5. Removal of Occluded Air.—Place the pyknometers in the 
desiccator, which should then be closed and attached to the water 
pump until the greater part of the air is expelled from the sys- 
tem. This takes from 5 to 10 minutes. Close the system with 
a pinchcock and attach the desiccator to an oil pump for the 
removal of the small amounts of air given off at the low pres- 
sures obtainable with the oil pump. The manometer is used to 


81 


82 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


indicate whether the oil pump is giving the proper vacuum. 
When the manometer indicates that the vacuum, which should 
be not greater than 3 millimeters, is constant, the oil pump 
may be cut off for short periods, precaution being taken that 
the vacuum does not change materially due to leakage. It will 
be noticed that bubbles of air come from the pigments very 
rapidly at first and that this action gradually decreases and 
finally stops altogether. The time required for complete re- 
moval of air varies from one-half hour to two hours, depending 
upon the nature of the pigment. When no more bubbles can be 
seen it is assumed that all the occluded air has been given off and 
the pigment thoroughly wet with kerosene. Air can then be 
slowly admitted to the desiccator by means of the pinchcock. 
(6. Filling and Bringing to Temperature—Take the pykno- 
meter from the desiccator and fill with kerosene, care being 


FIGURE 40 
Photo of Apparatus. 


taken to add sufficient to prevent the formation of air bubbles 
when placement of the thermometer is made. Place the ther- 
mometer in the water bath. Cool the bath with ice to between 
10 and 13° C. Place the pyknometer in the bath and allow it to 


SPECIFIC GRAVITY OF PIGMENTS 83 


come to constant temperature. Insert the pyknometer ther- 
mometer or capillary tube. Add enough warm water to the 
bath to raise the temperature suddenly to about 14.5° C. in order 
to expand the kerosene and prevent it from creeping down the 
capillary and admitting a small amount of air. Allow the bath 
to come to a temperature of 15.6° C. Wipe the capillary tube 
with filter paper and put on the cap. Read all temperatures on 
the thermometer in the bath and not on the thermometer in the 
pyknometer. Remove the pyknometer from the bath and dry. 


Smee E 
Wee este se Vy ss! 

—— a 
(l Cee Te Oe Olexe 


© 
wee ee He 


Weighing 
Bottle wit 
neck in 
Pyknometer 


FIGURE 41 
Apparatus Used in Work. 


Allow it to stand for one-half hour to enable it to come to room 
temperature. Weigh. It is advisable to allow pyknometer to 
stand approximately the same time before each weighing so as 
to compensate for slight errors due to evaporation at the joints. 

7. Precautions.—Before a new desiccator is first used it 
should be wrapped in a towel and tested under the vacuum to 
be used. Great care should be exercised in handling the desic- 
cator when the vacuum is on as any sudden jar may cause it to 
collapse. ‘a : 

8. Number of Samples.—It has been found convenient to run 
six samples at one time the desiccator specified being of the 
proper size to accommodate the above number. 


84 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


DESCRIPTION OF APPARATUS USED IN METHOD. 


A. Pyknometer. 
Type Al. 


Type A2. 
B. Water Bath. 


C. Manometer. 


D. Desiccator. 


Water Pump. 


E. High Vacuum 
Pump. 


F. Electric Motor. 


G. Weighing Bottle. 


Thermometer. 
Wash Bottle. 


Capacity 50 CC. 

Thermometer at neck, and capillary tube at side. 

A. H. Thomas Co. No. 46688. 

Central Scientific Co. No. 1730. 

Long, thin capillary tube at neck. 

Specially made by Eimer and Amend. 

Vessel filled with sufficient water to permit of only a 
very gradual rise in temperature. Equipped with a 
stirring device, preferably air blown, as the pyk- 
nometers are easily tipped over. 

Open tube Manometer to show vacuum obtained in 
desiccator. Made of 6 mm. diameter glass tubing 
filled with mercury to approximately 86 cm. fitted 
with pressure tubing attached to a Y tube lead- 
ing to desiccator and pump. 

Heavy Wall Glass. Desiccator constructed for vac- 
uum work, with hole at side. To withstand vacuum 
of one atmosphere. 

A. H. Thomas Co. No. 25834. 

Scientific Materials Co. No. 1919. 

Central Scientific Co. No. 3776. 

Laboratory water vacuum pump necessary to expel 
the greater portion of air in the desiccator. 
Scientific Materials Co. No. 2554, No. 2556. 

Central Scientific Co. No. 5476. 

Small vacuum pump to give vacuum of not more than 
3 mm. The Nelson Oil Pump is satisfactory. This 
pump has a displacement of approximately 200 cubic 
inches per minute or 7 cubic feet per hour at a speed 
of 900 R.P.M. It will evacuate a flask of one liter 
capacity to a vacuum of 1 mm. in two minutes. 
Scientific Materials Co. No. 143. vet 
To drive Vacuum Oil Pump. A constant speed type 
of motor is most satisfactory. If for D. C., a shunt 
wound motor, or, if for A. C. an induction motor. 
The most efficient speed is between 800 and 900 R.P.M. 
At this speed it gives as good results as when driven 
faster, and develops less heat. 

Weighing Bottle with cork. Neck to be small enough 
to fit inside the neck of the pyknometer. This is es- 
sential, as small quantities of pigment easily adhere 
to the ground glass joint of the pyknometer. 25 c.c. 
Babcock Milk Test Bottles are satisfactory after cut- 
ting off the neck to approximately 1% inches. 

A. H. Thomas Co. No. 33964. 

Scientific Materials Co. No. 4176. 

Central Scientific Co. No. 9104. 


Range 0° to 60° C. graduated in 1/10th of a degree. 
Ordinary water bottle type for kerosene. 


Note: The difference in levels of the mercury in the manometer when the 
system is in operation, subtracted from the barometer reading taken at the - 
same time, gives the vacuum of the system in millimeter of mercury. The 
difference between the barometer and the manometer should not exceed 


3 MM. 


SPECIFIC GRAVITY OF PIGMENTS 85 


EXAMPLE OF CALCULATIONS 


Standardization of Pyknometer 
Weight of bottle and water 


eres. = 88.2777 
AV elon. of? bottle. 2. = 33.3527 
Weight of water at 15.5° C............. = 54.9250 
Weight of bottle and kerosene = 77.9420 
Weient ot bottle.,.020 40. os. = 33.3527 


Weight of kerosene at 15.5° C. = 44.5893 


Specific gravity of kerosene = Ry Seg Oat ane eo by o118. 
15.5° C. 


Weight Water 54.9250 


METHOD OF CALCULATING RESULTS 


Let K = Weight of bottle filled with kerosene only. 

Let P = Weight of pigment used. 

Let F = Final weight of bottle with pigment and kerosene. 
Let S = Specific gravity of the kerosene used. 


PXS 
Then specific gravity of pigment =(PAlK) i 
Thus: 
Red Lead 
K = Weight of bottle filled with kerosene only = 77.9420. 
P = 16.0000. 
x = es weight of bottle with pigment and kerosene = 92.4826. 


16.0000 X .8118 


Sp. Gr. of sampl = ee = 
Pee Pp Ben’ Lead — (6.0000 + 77.9420), — 92.4806 8" 


Specific Gravity of Mixed Pigment. For calculating the specific gravity 


of a mixture of two pigments in definite proportions, when the specific 
gravities of each are known, use this formula: 


pe St 
100. ( Pp ) = specific gravity of mixture. 


Where P and P’ are the percentages of the two pigments and S and S’ 
are their respective specific gravities. 


Example: 
15 85 
Ud Cr rraary 
100 
100 = (8.48 + 14.56) = 99.99 — 


4.35 (specific gravity of mixture). 


METHOD FOR DETERMINING SPECIFIC GRAVITY OF PAINT LIQUIDS 


The specific gravity of a liquid may be determined with suf- 
ficient accuracy with a Westphal balance or a_ standardized 
hvdrometer and thermometer in the customary manner, mak- 


86 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


ing any necessary corrections for temperature. For viscous 
blown or bodied oils or for mixed paints, satisfactory results 
may be obtained, when a quantity is available, by weighing a 
liter of the oil or paint in a graduated tared liter flask. When 
only small amounts are available or when great accuracy is 
desired the method below* should be used: 

The specific gravity of an oil is expressed as the ratio of the 
weight of a given volume at 25° C. to that of an equal volume 
of water at the same temperature. The determination of 
specific gravity, in the case of heavy bodied oils especially, is 


i 
( 
\ 
' 
| 
1 

! 
| 

I 
I 

\ 
t 
4 
| 
i 
| 
! 
| 
1 
) 


FIGURE 42 
Pyknometer 
or weighing 
bottle. 


best made in a straight walled glass tube pyknometer approxi- 
mately 70 mm. long and 22; mm. in diameter, carefully ground 
to receive an accurately fitting glass stopper with a hole of 1.5 
to 1.7 mm. bore in place of the usual capillary opening. The 
stoppered tube should have a capacity of about 24 cc., and when 
empty should weigh not over 35 grams. 

The type of bottle described is illustrated. . 

The pyknometer with stopper is first calibrated by weighing 
it, clean and dry, upon an analytical balance. This weight is 
called A. It is then filled with distilled water at a temperature 
of 25° C., the stopper firmly inserted, all surplus moisture wiped 


* The above described method is adopted from the proposed tentative 
standard test for the specific gravity of road oils, road tars, asphalt 
cements, and soft tar pitches. See Proc. Amer. Soc. Test: Mater., Vol. XX, 
1920. 


SPECIFIC GRAVITY OF PIGMENTS 87 


from the surface with a clean, dry cloth, and again weighed. 
This weight is called B. 

For the determination of the specific gravity of an ordinary 
cil or paint liquid, the material shall be brought to a tempera- 
ture of 25° C. and poured into the pyknometer until it is full, 
using care to prevent the inclusion of air bubbles. The stopper 
is then inserted and the excess of liquid forced through the 
opening is carefully removed with a clean, dry cloth. The 
pyknometer and contents are then weighed, and this weight is 
called C. The specific gravity of the material may then be cal- 
culated from the following formula: 


C—A 


Specific gravity = 
p g Me Pen 


When the specific gravity of extremely heavy bodied oils or 
blown oils, or certain paste products is to be determined, the 
viscosity of these materials may make the previously described 
method inapplicable. Such materials should first be gently 
warmed, using care to prevent loss by evaporation. When 
fluid enough is poured into the clean, dry pyknometer to about 
half fill it. Precautions shall be taken to keep the material 
from touching the sides of the tube above the final level and 
to prevent the inclusion of air bubbles. It is advisable to 
slightly warm the tube before filling. The pyknometer and 
contents are then cooled to room temperature and weighed with 
the stopper. This weight is called C. The pyknometer is next 
removed from the balance, filled with distilled water, and the 
stopper firmly inserted. It is then completely immersed for not 
less than 30 minutes in a beaker of distilled water maintained 
at 25° C., after which it is removed and all surplus water wiped 
off with a clean cloth. It is immediately weighed. This weight 
is called D. The specific gravity of the material may be cal- 
culated from the following formula: 

C—A 


Specific gravity = (pl) aoe 


Average Specific Gravity Data.—For the convenience of 
‘manufacturers who do not have facilities for making specific 
gravity determinations on various types of pigments, and who 
desire a chart showing the average specific gravity of many of 
the commonly used pigments, a special table has been prepared. 


88 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


TABLE XIV—Table of Bulking Averages—Specific Gravity of Paint Liquids 


Weight One pound 


Specific per solid bulks 

gravity. gallon. gallons. 
Rew dinseed OG o.oo ie ae es eee . 932 7.764 . 1288 
Bodied ‘Linseed Oils coke oo ek ee .942 7.847 .1274 
Heavy Bodied Linseed Oil............. .98 8.163 1225 
Raw soya pean-Oilg ica tas con Bae ee .929 7.739 . 1292 
Rave Ting Oe ve eaten: Gare on .940 7.830 .1277 
**T quid: Painy Leer oct. 4 ions Fas pe .85 6.681 . 1497 
**Mixing Vaimishic 2. 455 220 4 oe cere .905 7.539 . 1326 
Taper iG. 4. yer cas ae tee eee 867 7.222 . 1385 
+8 Vineral Mpirite en atcas aGes wc ea 15 6.456 . 1549 
Benzo (oO pee oes a a . 882 7.347 .1861 
Benzine:(62>) eA kee eo eee eee 745 6.206 .1611 
Solvent Naphtha -(160") 0 cay es os . 902 7.514 . 1331 
Grain Aloohol7: 74 hee ve ee 185 6.539 . 1529 
Wood Alcoholii..4 neo s: eee ee 791 6.589 .1518 
ACOLONE Ds o's OG tes, hele 2 Op Ee Teel OE 6.639 . 1506 
Carbon: Petrachloride 2.4. a eee 1.60 13.328 .07502 
Amy Acetate oie ef ie sate eer .874 7.280 . 13874 
Ethyl Acetate: .. wah $4 oi eacce eee . 902 7.514 . 1331 


** These liquids will vary greatly in specific gravity. Grinders should determine 
the figure for the products they use. 


It should be pointed out, however, that the specific gravity of 
even such colors as are termed chemically pure, such for in- 
stance as chrome green, may vary to a great extent. This is due 
to the fact that these greens may contain a small or a large per- 
centage of blue, and in some instances varying amounts of lead 
sulphate. This variance in composition, therefore, of even 
chemically pure colors, is sufficient to warn the paint grinder 
that serious mistakes may occur in calculations made on average 
specific gravity figures of certain colored pigments. A chart 
is also presented showing the specific gravity and bulking values 
of many liquids that are used in paint and enamel manufacture. 


SPECIFIC GRAVITY OF PIGMENTS 89 


TABLE XV—Table of Bulking Averages—Specific Gravity of Some Dry 


Pigments 
Weight One Pound 

Specific per solid bulks 

gravity. gallon. gallons. 
Basic Carbonate White Lead........... 6.81 56.73 0.01763 
Basic Sulphate White Lead............ 6.41 53.40 .01873 
Ve LAS re Cae Wins A sea eae 5.66 47.15 .02121 
Zine Oxine, Leaded, 809%). ees. es 5.95 49 .56 .02018 
OT OMG tre ee aes ee ee 4.30 35.82 02792 
Bt ae ee ee hie i wc a 4.30 35.82 .02792 
AGN Sn Sie ee See ee 2.85 23.74 .04212 
Pee le Rs nee ee eee 4.45 Syem Urs .02698 
CRETE ONG a ere ass Us on 2.02 21.82 .04583 
Re TRS aw Lo Ring ee Oe 2.65 22,07 .04531 
REY Sy eg Lg eee ee 2.84 23.66 .04227 
VU ORs ee ee tees Sa Kang nk fe Dave ee Aaa 04431 
*Venetian Red, (20% Fe.O3).........+- 3.05 25.41 .03935 
Red Oxide, (40% Fe:Os)..........--+-- 3.45 28.74. .03479 
Red Oxide, (95% Fe:Os)..........-.--- 4.95 41.23 .02425 
Indian Red, (90% Fe2O3)...........--- 4.92 40.98 02440 
Ferric Oxide, (98% Fe2O3)...........-- BeLD 42.90 .02331 
Pelee ee ee tas, aa cs be We 3.95 32.90 .03040 
STE. ON A a cae ee ea a 2.80 23.02 .04288 
Sienna eta Woe ie sta ee. o's 3.27 27 .24 .03671 
Pee GRt Mrs Gee ets. Sein aie 3.957 32.90 .03040 
Met yl kaa or Sess ee te ne a 2.68 22200 .04480 
ete AE ee ss Skee he oes 3.80 31.65 .03160 
Brown Oxide, (50% Fe2O3)..... ae a 3.35 ZL LOl .03583 
Mineral Brown, (45% Fe:O3).......... 3.34 27.82 .03595 
yori S10 te to eek pee Ses 4.95 41.23 .02425 
VETTING, °c, Bice Rae ioe re a ee en a 9.40 78.30 .01277 
(rane Wierda Gees agi ee nee Ss 8.80 73.30 .01364 
ee eae) ye in si eae Be 8.80 73.30 .01364 
Pere BE Oe ONet Serta tae 8 ae a Ek gs ae 1250 12.50 .0800 
Para Red 10% (on Lime and Barium Base) 2.65 22.07 .04531 
Pure Toluidine Red Toner............. a 49 12.41 .08058 
Tel orien a 5 1a Coe an ee ar { as 
hel oCa( VINE iS oie uh payee eee BETS 22.91 .04365 
PCPTO CI GTORIG iss. o's ok eet Ve 2.80 23 .32 .04288 
PC Go ree. ee ns 2 ie os lela ke 1.85 15.41 .06489 
it eramarine WIG cans Fe oc se ee ews 8 2.35 19.58 .05107 
BU brome Velow Get 3. 5. eee et *6 00 
VERA SURO, eo G GU es cue ee pe ee {278 14.83 .06743 
OP y sient oil Se on a ces 1.81 15.08 .06631 
Ps cr Ga hia he ve ee eal 2.64 21.99 .04548 
eee ere re ek os ee G's ay ie 2.36 19.66 .05086 
Weewetoueebaletas. 6. ob occ ct oe dy eS 2.701 PAE .04431 
Pane ce ee os ad ep oO 7.06 58.81 .01700 
PAT ORITITID UI sae cs ce wl ee Ew 2.64 21.99 .04548 
ORL UIs Pele ec) oo ioe snes V vind de a ae 11.09 92.38 .01082 


* These will vary widely according to composition required for shade or tone and 
character of base. 


— SS = Ty, -;” CL 


EXAMINATION OF PAINTS, VARNISHES AND COLORS 


90 


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CHAPTER XI. 
DETERMINING THE FINENESS OF PAINT PIGMENTS 


There is given below the method developed and standardized 
in the writer’s laboratory for the determination of the fineness 
of paint pigments. This method was originally published in 
Scientific Section Circular No. 148. 

(a) Reserve in the laboratory a standard 325-mesh screen* for 
comparison purposes. Whenever a new screen. is secured, a 
practical test of its accuracy should be made by running on it 
and on the standard screen a pigment that has a considerable 
percentage of coarse particles. A reserve stock of such pigment 
should be kept for this purpose. 

(b) Weigh the screen upon an analytical balance, recording 
the weight in a figure carried to the third decimal place. Then 
wet the screen on both sides with the liquid to be used for wash 
purposes. 

(c) Weigh upon a piece of paper or a tared watch glass, a 
sample of the pigment to be tested. For most pigments 10 


*Sieves 3 inches in diameter will be received by the Bureau of Standards 
for test. The cloth will be tested to determine whether or not it conforms 
to the specifications for cloth of the U. S. Standard Sieve Series. The 
specifications for the sieve frame are now being prepared. No. 325 cloth 
of the U. S. Standard Sieve Series should be made of wire 0.036 mm. 
(0.0014 inch) in diameter, a tolerance of 20 per cent being allowed at 
present for this diameter. The average opening between adjacent parallel 
wires should be 0.044 mm. (0.0017 inch) the tolerance being 7 1% per cent 
with the additional limitation that the maximum opening shall not exceed 
0.044 mm. by more than 60 per cent. Sieves whose cloth conforms to these 
specifications and whose frames are in accordance with specifications 
now in preparation will be marked with the letters “BS” and the year 
in which the test is made. A report will be issued for each sieve submitted, 
a nominal fee being charged for this test. 

For those who desire to investigate the subject further the following 
references are given: 

The classification of Fine Particles According to Size. By G. W. Thomp- 
son, Proc. A. S. T. M., Vol. X, 601 (1910). 

Kolloid Zeitschrift. Vol. 18, page 3348, 1916. 

Rapid Test for Fineness of Paint Pigments. By Dr. C. D. Holley and 
J. C. Brier. Drugs, Oils and Paints, May 10, 1915. 

Comparative Tests for Fineness of Pigments. By Dr. ©. D. Holley. 
Paint, Oil and Chem. Review, No:?2s, 1921. 

Circular No. 90. By H. A. Gardner, Scien. Sec., Educat. Bur., Paint 
Mfrs. Assn. U. 8S. 

A Photomicrographic Method for the Determination of Particle Size of 
Cana Rubber Pigments. By Henry Green, J. Franklin Inst., 192,637 

See also “Optical Properties of Pigments,” H. E. Merwin. Proc. A. S. 
T, M., Part II, 1917, page 496. 


91 


92 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


FIGURE 43 
Standard 200-Mesh Screen X-50 Unused. 


Pe eSUETB SB Eeeseesees 
BSP HERE RNBeeeeseeeee) 
SEUSS EBUBMBEPeBeaeeaewea sane 
TR RPERRERE SEER ERE SE EERE 
BSeoeean (Bee Peeaeeeaee 
aE "SUBUSBRBRERBESRERBBBHS 
eenee’ 2B SPE Ceasar 
“TUPPER PERE EP PURER REE EPG 
BEB SUSE eee 
SUS=@SEUSBBSEUEBEEEzA 
POT R PURER ULE PY F 
SUGERRERBRT ERE GZ 
eaueeusan: 


FIGURE 44 


Standard 325-Mesh Screen X-50. 
Used 4 Times. Note Pigment Particles Retained. 


FINENESS OF PAINT PIGMENTS 93 


grams will be the proper quantity. For black pigments of low 
specific gravity, 2 grams will be sufficient. For pigments like 
Prussian blue and graphite, 3 grams are generally used. The 
pigment may then be transferred to the screen. 


If the pigment is one that is difficult to wet with the wash 
liquid, the quantity weighed out should first be placed in a beaker 
containing some of a liquid ithat easily wets the pigment and 
that is miscible with the wash liquid. For instance, if water is 
to be used as the wash liquid, alcohol may be used as the wetting 
medium. The pigment is then gently stirred with the wetting 
liquid and the contents of the beaker transferred to the screen. 
Where small particles of pigment are retained on the stirring 
rod or walls of the beaker they may easily be removed with the 
brush. 

(d) The screen is then held under a tap (A) delivering about 
300-500 cc. of wash liquid per minute. By slightly shaking 
the screen, the pigment will be rapidly carried through. A 
soft camel’s hair brush may be used in aiding the operation. 
If the screen is! held at a slight angle so that the pigment will 
gradually collect at one edge during the washing process, and 
then rotated, the pigment may be brushed out rapidly, with no 
risk of clogging the screen. | 

(e) After the majority of the finely divided portion of the 
pigment has passed through the screen (from two minutes to 
an hour, according to kind of pigment), the screen is placed 
in an 8-inch porcelain dish (C) containing 250 cc. of the wash 
liquid. The screen will thus be covered to a depth of about 
one-half inch. The pigment remaining on the screen may be 
brushed with a soft l-inch camel’s hair brush at the rate of 
two strokes per second during two periods of 10 seconds each. 
The screen is then raised from the dish after each 10-second 
period to let the liquid on the screen run through. Change the 
liquid in the dish after every two brushing periods described 
above. Continue this operation until typewritten letters can 
be read through a layer of the wash liquid 8cm. thick, which is 
approximately the height of a filled 250 cc. beaker of the usual 
laboratory type (D). 

Occasionally pigments will be found that foam when water 
is used as the wash liquid. In such instances, during the last 
washing in the porcelain dish, the use of a liquid that breaks 


94 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


FIGURE 45 


FINENESS OF PAINT PIGMENTS 95 


down the foaming and is readily miscible with water, such as 
alcohol, will usually overcome this drfficulty. 

(f) Now wash back on to the screen the pigment particles 
adhering to the brush. Wipe off the water below the screen. 
Add a few drops of alcohol and then of ether to expedite drying. 
Dry the screen in a water bath or on a radiator, and weigh. 


(g) For pigments requiring wash liquids such as turpentine 
cr mineral spirits, use apparatus shown in (B). This apparatus 
is also used for determining the fineness of paste paints ground 
in oil. For paints containing varnish, such for instance as 
Japan colors, a wash liquid of turpentine, solvent naptha or 
similar solvents is necessary depending on type of pigment 


96 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


and varnish. Always finish with ether to remove traces of 
heavy wash liquids such as turpentine which might dry to 
resinous film. . 

Discussion of Method.—A slight source of error in the above 
method may result from the fact that the opacity of a small 
quantity of pigment in the wash liquid is dependent not only on 
the optical constants of the pigment and liquid but also on the 
size of the particles. In other words, a certain degree of opacity 
may be produced by varying the amount of pigment. However, 
the error has been found to be extremely slight, and the method 
is very much more rapid than that at one time suggested, of 
drying and weighing the screen at a number of intervals during 
the brushing operation, to constant weight. This latter method 
would be very tedious and cause great loss of time. 

Occasionally pigments will be found that contain quantities 
of soft lumps or aggregates of finely divided particles which 
have been cemented together by moisture or by over-heating 
during the drying process. All of these lumps will not pass 
through the screen even with brushing, as the brush is too 
soft to break down the aggregates. Placing these lumps be- 
tween the fingers and exerting slight pressure on them will 
readily indicate whether they are single coarse particles or 
aggregates of fine particles which may be broken down by 
slight pressure. In the latter instance, the lumps during the 
processing should be spread out in a glass petri dish and broken 
down with a spatula, using slight pressure but no grinding 
action. The contents may then be returned to the screen with a 
wash bottle. In this way a great amount of time can be saved 
and accurate end points and readings obtained. 

It was found that certain pigments, such as white lead and 
lithopone, very often show a cementing together of particles 
that may be due to the presence of water-soluble metallic salts. 
Although continued soaking in water would ultimately break up 
such aggregates, it was thought that the use of water as a wash 
liquid, would be inadvisable. This is due to the fact that oil is 
used for factory grinding and a similar liquid should be used 
for pigments having cemented particles, when running a screen 
test. For such pigments, therefore, wash liquids consisting of 
mineral spirits, turpentine or kerosene have been recommended. 
Some may still prefer to use water, so results on both are given 
in the charts. 


FINENESS OF PAINT PIGMENTS U7 


Again, with such pigments as Prussian blue a curious state 

of hard aggregate formation may be observed. While washing 
with water would break up such aggregates (peptization some- 
times occurring), and in most instances show a residue of less 
than 1 per cent, washing with kerosene or liquids in which these 
axgregates were not broken up would leave residues as high as 
6Z per cent. 
+ In view of the widely varying resulis when solvents other 
than water are used, it is probable that no limit can be set for 
the percentage of residue from Prussian blue, when using liquids 
other than water. The use of mineral spirits will undoubtedly 
indicate to grinders what blues are best suited for rapid grind- 
ing in oil, but until color makers are able to wash and dry 
Prussian blue in such a manner as to prevent the formation 
of aggregates, it is probable that no standards within close 
limits can be set. 

Photomicrographs of Pigments.—Six of the photomicro- 

graphs of the coarse particles in pigments, shown in this chap- 
ter were made by a rather novel method discussed in one of the 
writer’s Articles on Fineness. By this method a very rapid ex- 
amination of pigment particles can be made, especially if they 
are of coarse grain. Instead of requiring a long time for the 
preparation of special slides, special illumination, etc., all that is 
required is a Victrola or similar talking machine record and a 
microscope. (See Figs. 47-52.) 
. The test is made by rubbing with the finger a portion of the 
pigment across the grooves of a disc phonograph record and then 
observing the surface with a microscope. The Edison type of dise 
has a spiral groove with 150 convolutions per inch of radius. 
The lines are 1/150 of an inch from centre to centre. The radius 
of curvature of the sound grooves is 4/1000 (.004) of an inch. 
The average depth of the grooves is 1/1000 inch. i 

One record may be used for several pigments which may be 
numbered and the records kept in a cabinet for comparison as 
standards for various subsequent batches of pigments produced 
or received in the factory. During the procedure of rubbing the 
pigments into the grooves, characteristic differences are at once 
noted. Some pigments will feel coarse and gritty. Others will 
have a soapy or unctuous feeling. For instance, two samples of 
china clay or barytes which appear to be of equally fine texture 
when rubbed between the fingers, may upon rubbing into the 


98 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


FIGURE 47 


Red Lead. 
Some Particles Are Transparent. 


FIGURE 48 
White Lead. 


FINENESS OF PAINT PIGMENTS 99 


FIGURE 49 
Barytes. 


FIGURE 50 


China Clay. 
Note Transparent Particles. 


100 EXAMINATION OF PAINTS. VARNISHES AND COLORS 


FIGURE 51 
Calcium Carbonate. 


FIGURE 52 


Bone Black. 
Note Angular Hard Particles. 


FINENESS OF PAINT PIGMENTS 101 


record show entirely different characteristics. One pigment may 
feel soft or “silky” in texture, while the other may feel granular 
and “gritty.”? Microscopic examination of the surface will then 
immediately disclose the reason for this phenomenon. 

Most pigments are made up of particles of varying size. The 
large particles are often covered with fine ones. When such pig- 
ments are placed on a record, the rubbing action forces the large 
crystals between the grooves and arranges them with their facets 
parallel to the face of the record. The fine particles are at the 
same time wiped from the larger crystals, so that the form of 
the latter is disclosed. With fume pigments, the very fine par- 
ticles as well as the agglomerates may be shown. The relative 
degree of color, whiteness, and hiding power of the pigments 
are to some extent also indicated. © 

For the microscopic examination it is advisable to use a 32 
mm. objective and a 12.5X eye-piece. Greater depth of focus is 
thus obtained and the magnification is sufficient. It is usual to 
look at the disc obliquely in order to get the specular reflection 
of the light. 

For a photographic record of the appearance of the pigments, 
great care should be taken that a strong light is provided and 
that a water cell is interposed for absorbing the heat rays of the 
light. Otherwise the light, impinging upon the record at one 
point, will cause a melting down of the grooves. Photography 
then becomes impracticable. . 

While the author has referred above to a simple method he 
uses for the making of photomicrographs of pigments of rela- 
tively coarse particle size, the most approved method of making 
photomicrographs of finely divided pigments is that developed 
by Henry Green.* A brief abstract of Mr. Green’s method is 
presented below. 


THE METHOD 


The fundamental idea involved in the method is by no means 
a new one. In all probability is has been employed many times 
by various investigators and for numerous purposes, yet the 
author is not aware of a single case where it has been sufficiently 


* “A Photomicrographic Method for the Determination of Particle Size 
of Paint and Rubber Pigments,” by Henry Green. J. Franklin Inst., 1921, 
p. 638. Also “The Microscopy of Paint and Rubber Pigments.” Research 
Bulletin, The New Jersey Zinc Co., Palmerton, Pa. 


102 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


developed in detail so as to make it of practical importance in 
the special line of work to which it is here applied.* 

Briefly stated, the pigment is prepared in such a manner so 
that a photomicrograph, at a known magnification, can be taken, 
showing clearly and distinctly the individual particles, which 
are then measured from the negative by a method to he de- 
scribed presently. 


PREPARATION OF THE SAMPLE FOR PHOTOGRAPHING 


About a milligram of the pigment is placed on the center of a 
microscope slide to which is added a drop of redistilled turpen- 
tine. The slide is to be held at the two ends between the thumb 
and first finger; a glass rod, with smooth, straight sides, so that 
it will come in close contact with the glass, is now used to dis- 
perse and rub out into an’extremely thin layer the material in 
the turpentine. This is best accomplished by a forward and 
backward motion of the rod in the direction of the length of the 
slide and extending over the central area only. The rubbing 
must cease at a certain critical stage, when there still remains 
sufficient turpentine unevaporated to prevent the mount becom- 
ing “streaky,” and yet not enough to float the particles which 
would allow them to flocculate. By a slightly upward flourish 
of the rod on the last stroke the mount can be made wedge shape, 
that is, dense in one part and thin in another, with all inter- 
mediate grades of density between. In this way it becomes pos- 
sible to select a section for photographing that will show neither 
too many particles nor too few per given unit area.7 

*The method of grain measurement exployed by metallographers is 
fundamentally similar to the photomicrographic method of particle meas- 
urement. Note on grain size, by G. H. Gulliver, J. Inst. of Met., 1918. 

“The Determination of Grain Size in Metals,” by Zay Jefferies, A. H. 
Kline, and E. B. Zimmer, Trans. Am. Inst. Mining Engineers, 1917. 

+ This method of dispersing the particles is to be used principally with the 
finest pigments, such as zinc oxide, lithopone, white lead, etc.. In the case 
of these materials it will be found impossible to produce any grinding effect 
that will cause the individual grains to be broken up into smaller ones. 
This is on account of the fact that neither the glass slide nor the rod are 
optically flat, and consequently they are unable to come in close contact with 
each other except at a very few points. 

With coarser materials such as clays, barytes, asbestine, etc. (which will 
probably feel gritty), only the slightest possible pressure must be brought 
to bear upon them with the dispersing rod for here there is some danger 
of a real grinding effect becoming manifest. Fortunately, these materials 


are so large that flocculation does not prevent the outline of the particles 


from being seen and a measurement made, hence, very little rubbing is nec- 
essary. 


FINENESS OF PAINT PIGMENTS 103 


The next step, after the material is properly dispersed, is to 
completely remove the remaining turpentine. This should be 
done by laying the slide on a hot plate, the temperature of which 
is sufficiently high to cause evaporation within forty or fifty sec- 
onds. Care must be taken that volatilization is complete. This 
is satisfactorily ascertained by noticing if any odor of turpen- 
tine remains after heating. The particles will now be found to 
be cemented to the glass and should remain in this condition, 
if a reasonable amount of care is exercised in handling the slide. 
When sufficiently cooled a small drop of glycerine is placed on 
the center of the mount and then covered with a thin slip. The 
excess glycerine must be carefully squeezed out at the sides of 
the cover glass and absorbed by filter paper. The mount is 
finished in the usual manner with a ring of Brunswick black. 

If the above instructions have been properly carried out, and 
the mount now held to the light, the pigment, if its index of 
refraction is high, will just be perceptible as a faint cloud; if 
its refractive index is low, the pigment will be entirely invisible, 
except with a miscroscope. 

Upon microscopic observation three essential conditions should 
be manifest. They are— 

1. The particles will be in one plane. 

2. They will be free from Brownian motion. 

3. They will be dispersed, showing individual grains instead 
of aggregates and flocculates. 


THE PHOTOGRAPHY 


It is not the purpose of the present paper to describe the 
method of using a photomicrographic apparatus. It is also 
hardly necessary to add that unless one has acquired consider- 
able facility in the manipulation of such apparatus it would not 
pay to attempt its application in the measurement of particle 
size. 

In regard to the present problem, however, it must be stated 
that all photographs are made with transmitted light, and that 
this light is to be absolutely axial. Obliquity of illumination will 
give a distorted image, causing an appreciable error in the 
results. 

The beginner will find it advantageous to start with a fine- 
grained contrast plate, using hydroquinone developer. After he 
has obtained experience in handling these materials successfully, 


104 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


he should then try his ability with panchromatic plates and de- 
velop with pyro. There are plates of this kind made especially 
for photomicroscopy which give great detail together with suffi- 
cient. contrast. 


avi x 
Jt v, ha sen 
& & - tor e $n, 
25 ° ° al BD b 
te * ue ‘ went - 


3 . & +? ° 
Ps: AD *, * : 3 ei 
24, «& > * BR A y& 2 
“thet @ es; * i ee ae 
S Pa F - 2 & “: jo rd 
v2, y¥? “ 4 i erst een 
oo Tee ee Plies Ie? 
¥ 2 8 mu oe 
w os Py: ~~ of | 
ee Me x 
as es 
ra ¢ 
vt cy 
FIGURE 53 FIGURE 55 
American process zine oxide Basic carbonate of white lead, 
taken at 1,500 diameters, showing 1,500 diameters, showing the char- 
the characteristic crystalline out- acteristic hexagonal outlines of 
lines. these crystals. 


bois es ee * Cee 

FIGURE 54 FIGURE 56 
French process zine oxide, 1,500 Basic sulphate of white lead 
diameters. There is less tendency (sublimed white lead), 1,500 
here to form needles and twins diameters. There is a slight ten- 
than in the American process zinc dency, not well shown in the 
oxide. photograph, for this pigment to 


form cubes. 


FINENESS OF PAINT PIGMENTS 105 


FIGURE 57 FIGURE 58 
Gas Black, 1,500 diameters. Barytes, 800 diameters. 


Taken with 1.7 mm. quartz mona- 
chromat and ultra-violet light. 


THE MAGNIFICATION 


Generally, in photomicrographic work, definition of structure 
is the one essential quality most desired. However, as the struc- 
ture of a pigment particle will give us no information in regard 
to its size, the factor, definition, may be neglected here to a 
certain limited extent.* On account of this fact it has been 
found an advantage to employ a magnification which otherwise 
would be too high if the best definition is to be obtained. Never- 
theless, care must be taken that the photographic image of the 
particle gives edges sharply enough defined so as to make a satis- 
factory measurement possible. 

With a 2 mm. apochromatic objective a magnification of 1,500 
diameters will be most convenient for pigments such as zinc 
oxide, lithopone, red oxide of iron, sublimed white lead, corroded 
white lead, Mathewson white lead, etc. Lower magnifications 
are used, naturally, with coarser materials. 


* But to no greater extent than is shown in the photomicrographs. 


106 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


FIGURE 59 


Gardner Photomicrographic camera used for making low magnification 


photomicrographs of exposed test panels on racks or fences. Tripod and 
film pack used. 


CHAPTER XII. 


OIL ABSORPTION OF PIGMENTS 


In mixing a pigment and a liquid a point is reached where 
independent of such mechanical forces as could be developed by 
actual grinding, the surface of each pigment particle is thor- 
oughly wet by the liquid and the pigment mass becomes thor- 
oughly saturated. This point represents the oil absorption 
property of the pigment, and is expressed by a factor termed 
the oil absorption factor. This factor is therefore a measure 
of the quantity of a given oil or liquid, required to thoroughly 
wet all the absolute particle surface of the pigment mass. The 
factor is ascertained by determining the number of cubic centi- 
meters of liquid required to saturate 20 grams of pigment. It 
is then expressed as the amount required for 100 grams of pig- 
ment. 

The factor obtained by this method should not be confused 
with that obtained by the older method of rubbing and mulling 
10 grams of dry pigment on a plate with oil gradually dropping 
from a burette until the point is reached when a workable paste 
is formed. The latter method gives an entirely different figure, 
more representative to the amount of oil required to grind a pig- 
ment to stiff paste form. The method given in this chapter gives 
figures more representative of the amount of oil required in 
what might be termed a stiff paint. Lithopone and other pig- 
ment makers have had difficulty in getting inspectors to use a 
common method that could be run in a specified manner, so that 
results will be reported uniformly. The method below is for that 
reason coming into wide use. 

The oil absorption of a pigment is particularly important to 
the manufacturer who wishes to maintain a product of uniform 
quality and to the user who desires such a product. For instance 
a user of lithopone might require for a certain paint, a pigment 
of a certain well defined oil absorption, in order that his product 
would remain uniform. If a shipment of markedly higher or 
lower oil absorption should be sent to him, he could discover 
this fact by the oil absorption test, previous to storing or using 
the pigment. 

In designing a paint the oil absorption factor is especially 


107 


108 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


valuable for determining the amount of oil required to grind 
each pigment to paste form or the quantity of each pigment re- 
quired to produce a certain desired consistency. In improving 


al 


Ht 


sine gontecomcimoereiar Nabe tlm scrineta ss trtmtrnnemnassheen-torantemeitnech teint 
tliat in is f 


FIGURE 60 


Apparatus Required for Determining Oil 
Absorption of Pigments. 


the properties of an existing paint, a consideration of the oil 
absorption factor is also important. Thus if it is desired to 
increase the consistency of a paint without increasing the per- 
centuge of pigment, high oil absorbing pigments may be used. 


OIL ABSORPTION OF PIGMENTS 109 


The opposite may be accomplished by the use of low oil absorb- 
ing pigments. In using high oil absorbing opaque pigments, 
inert pigments of low oil absorption may be added in order to 
lessen the amount of oil required to suspend the other pigments. 
When it is desired to secure maximum opacity, regardless of 
other qualities, a low oil absorption opaque pigment may be used. 
If a glossy enamel-like finish is desired, a pigment of high oil 
absorption is indicated. 

The amount of oil required for pigment saturation or wetting 
is directly proportional to the specific surface* of the pigment 
mass, existing at the point of saturation. As the specific surface 
of the mass is relative to its degree of particle sub-division or 
fineness, it also measures to a great extent the fineness of the 
pigment. The oil absorption factor being relative to the surface 
conditions of the pigment is independent of its chemical com- 
position or specific gravity. The practical advantages of know- 
ing the oil absorption factor lie in the information it gives con- 
cerning the following physical conditions of the pigment: 

(a) Relative amount of surface in the pigment mass. 

(b) State of sub-division of the pigment particles. 

(c) Comparative specific surface of various pigments. 

(d) Variation in fineness or particle sub-division of various 
lots of the same pigment. 

The property of absorbing a given quantity of oil is relative 
to the specific surface of the pigment mass. Thus the difference 
in oil absorption and body imparting property shown by various 
pigments is due to the difference in specific surface or particle 
sub-division. From, this it follows that the variation or differ- 
ence in pigments in this respect exists up to the saturation point 
only. Beyond this point they all become uniform in the amount 
of oil required to bring the mixtures to a certain consistency. 
This fact is improtant in the comparative testing of pigments in 
liquid paints. The following is illustrative of its application. 

If a series of pigments are ground into pastes on the basis 
of the individual oil absorptions of each, and the same amount 
of thinning mixture is then added to the same weight of each 


* It is believed that the oil absorption of a pigment may be reduced by 
compacting. The small particles would then form aggregates and the 
specific surface would be reduced, thus reducing the oil absorption. Sim- 
ilarly, by effecting electrical changes in the particles to cause a coalescence 
or by effecting a change in the surface tension of the particles, a reduc- 
tion in oil absorption might be accomplished. 


110 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


TABLE X VI—Oil Absorption Factors on Some Pigments 


Low-Oil High-Oil Average 
Pigment. _ Absorption | Absorption Type. 
| Type. Type. 

Basic Carbonate White Lead........... 15 22°09 “= 1a 
Basic Sulfate White Lead.............. 26 32 30 
PIO ORGS aria ene eh ahem Ae array ee 47.6 54.1 52 
Titangx.. tee wae kase SUR eae ots 22 28 26 
token Reeth eles rhs LOR goa AO eee | Gea | 31.3 36.5 32 
LAthOpones Pier noe ae A es) Gee 22.75 38.5 33 
Aslestine wa. coh; fa 'ae eect ea keer. neem 32 50 50 
Bargies. 607 oi a is ae ee cae ee . 13 15 13.5 
Blavie Vixens. ee ee ae eee | 23 36 30 
CBiria clay bre it oes ae ee ce ase ee | 41.5 53 51 
CY DRUIN ace acetal ear es ae | 26 35 33.9 
Pilied. (Crveta line ss coc mae at reas . 20 28 “eo SBS 
silice LAmorphousjied..-0. 04 28 be awa . 30 38 32 
Trade passa clones! Oi a ee ew Gate eae 40 65 60 
Wihitino cn ik + eee ee ee eee . 28 35 32 


dry pigment in its paste form (pigment plus oil required to 
saturate), the resulting mixed paints, barring thickening due 
to any chemical action, will be of practically the same con- 
sistency. 7 

Considerable information is also obtained by studying the 
condition of the pastes at the oil absorption point. A very 
considerable difference will be noted in the characteristics of 
the pastes produced by various pigments. Some pastes will be 
short and tough. Others will be long, stringy and soft. Some 
will have a high gloss. Others will present a dull appearance. 
Some of the pastes will be dense, requiring heavy pressure to 
flatten them out. Others will be soft and easily spread. The 
amount of oil absorbed does not entirely control these factors. 
In other words, two pigments of practically the same oil absorp- 
tion may yield entirely different types of pastes. For example, 
one may be dense and the other soft. These physical charac- 
teristics all indicate certain pigment qualities. 

The oil absorption point varies with different pigments and 
is influenced by certain conditions. A pigment in its dry state 
consists of individual particles and agglomerates of particles. | 
The particle surface and the mass particle surface combine to 
make the absolute surface existing in a given volume of the 
pigment. As the amount of oil required to saturate a certain 
amount of pigment is the amount required to wet the absolute 


OIL ABSORPTION OF PIGMENTS Tit 


particle surface, any influence which tends to change the sur- 
face content (by changing the specific surface) varies the oil 
absorption point. Two common influences accomplishing such 
change are found in the dispersion effect of certain vehicles, 
and the effect of mixing and grinding pressure. While these 
influences are always present to some degree in all paint mak- 


TABLE XVII 
Raw Linseed Oil Soya Bean Oil Colloidal Condition 
Oil 
Pigment. 
Oil Ab- | Character | Oil Ab- | Character | Oil Ab- | Character 
sorption of Paste. | sorption! of Paste. | sorption of Paste. 
Factor. Factor. Factor. 
Zine Oxide....... 54 Smo. = 9a Same as | 56.5 | Glossy. 
Glossy. with Smeary. 
Quite Linseed Quite 
long. Oil. rubbery. 
Leaded Zinc 30.0. |) solt, 35:5 | Same as 39 Quite 
Oxide (35%). with glossy. 
Linseed Smeary. 
Oil. Rubbery. 
Slightly 
granular. 
Lithopone (High | 37.5 | Short. ot Same as 38 Fairly 
Oil Absorption). Chalky. with glossy. 
Smooth. Linseed Long but 
Oil. not 
tough. 
Slightly 
granular 
In appear 
ance. 3 
Lithopone (Low | 25.5 | Soft and 23.5 | Sameas , 26 Very soft. 
Oil Absorption). Long. with Runny 
Fair gloss. Linseed and 
Contains Oil. smeary. 
large Good 
lumps. gloss. 
Lumpy. 


ing procedure, the basis of the oil absorption factor should be 
the condition of the pigment in its dry form with the elimina- 
tion of these influences to as great an extent as may be pos- 
sible. The oil absorption factor of all pigments is changed to 
the same relative degree by the introduction of these influences 
to an equal extent. 

Certain oils and liquids, due to surface tension phenomena 


112 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


or to such colloidal conditions as effect adsorption or develop- 
ment of great surface, tend to cause either a coalescence of the 
pigment particles into particle agglomerates or by their dis- 
persion effect, to break down the existing agglomerates and dis- 
perse the particles into an extremely fine state of sub-division. 
Either of these conditions change the specific surface of the mass 
and accordingly change the oil absorption point. This variation 
in oil absorption with different oils is illustrated by the follow- 
ing table, which gives the oil absorption factor of several pig- 
ments in linseed oil, in soya bean oil, and in a liquid having a 
relatively high colloidal viscosity but with an apparent viscosity 
approximately the same as the other two. 

Selection of Test Liquid.—In view of the results shown in 
the above chart it is important that the oil used for determin- 
ing the oil absorption factor be one that will have the minimum 
effects in causing either a dispersion or coalescence of the pig- 
ment particles. In such a vehicle the pigment tends to form a 
mechanical suspension or mixture only. Thus the degree of 
particle sub-division or agglomeration existing in the dry pig- 
ment is retained to the greatest extent. Of the common and 
available oils, raw linseed oil is the best suited for the pur- 
pose. With most pigments it has but little dispersing or coalesce: — 
ing effect. It is therefore used as the standard vehicle for de- 
termining the oil absorbing property of a pigment. If, however, 
it is desired to determine the oil absorption factor with certain 
other liquids, the results will be relative to the dispersing effect 
of the liquid used. In following the standard procedure a well 
settled Raw Linseed; Oil, clear and free from foots and having 
an acid value of from one to three should be used. An oil of 
this kind is readily obtainable and easily kept. A, variation in 
the acid value of the oil affects the oil absorption point; the 
amount of oil required increasing with an increase of the acid 
number. This difference is due either to a greater particle dis- 
persion or to a thickening caused by the formation of soaps. 
It is important, therefore, that in making determinations where 
very accurate results or close checks are desired, that the oil 
used be always of the same acid value. ; 

Effect of Moisture on Test.—The moisture contained in the 
pigment, between certain limits, seems to play no important part 
in the determination, since check results may be obtained on 
portions of the same sample of pigment whether air dried, oven 


OIL ABSORPTION OF PIGMENTS 118 


dried or even slightly moist. Therefore, the ordinary air dried 
sample of commerce is in a satisfactory condition if it does not 
contain sufficient moisture to cause it to mat together or cake. 

The temperature of the relatively small amount of oil used 
during the operation is not important, because the oil is im- 
mediately cooled by coming in contact with the much larger 
mass of pigment. This statement is made with the assumption 
that the oil is of the temperature prevailing in the ordinary 
laboratory. When, however, the pigment is quite warm, the oil 
absorption is slightly decreased. This is due to the fact that the 
viscosity of the oil is decreased by rise in temperature and con- 
- sequently the thickness of the film with which it wets the 
particles would be decreased. However, the difference between 
70° and 100° Fahrenheit, which is the average range of a 
laboratory, is very slight so that the temperature need not be 
taken into consideration except during extremes in either way. 

Principles to be Observed in Test.—The principle of this test 
is that of effecting the wetting of all the “particle surface” or 
“narticle agglomerate surface” of the pigment mass without the 
application of mixing or grinding pressure. This is accom- 
plished by certain oil addition and stirring procedure as de- 
scribed herewith. In all stirring operations, care must be taken 
not to cause mixing of the pigment and oil by applying pressure, 
as this factor will tend to vary the results. All stirring and 
mixing should be done very carefully and lightly. A finger and 
wrist motion is all that should be used, allowing the forearm to 
rest quietly. 

When the oil first comes in contact with the pigment, a cor- 
responding amount of particle surface is wetted. The particles 
thus wetted then coalesce or cling together and form agglo- 
merates or lumps of paste consisting of oil and pigment. These 
small lumps of paste should be kept distributed through the 
mass by stirring. As the absorption of oil by the mass increases 
these lumps will mat together, forming larger lumps or. balls of 
paste. With further absorption of oil by the mass, these larger 
lumps or agglomerates of oil and pigment paste will coalesce 
‘and with most pigments will form one large ball. (With a 
certain few pigments this large ball is not formed; the separate 
smaller lumps remaining separated.) After this point is reached 
a small amount of dry pigment may still be left around the bot- 
tom and Jower parts of the container. This pigment is wet by 


114 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


bringing it in contact with the free oil existing on the surface 
of the large ball or lumps of paste. The end point of the de- 
termination is reached when all of this dry pigment has been 
taken up and wet. This point is indicated by the following con- 
dition. While any dry unsaturated pigment still remains, the 
paste will not smear on the glass. At the point, however, where 
all of the pigment particles are wet, the paste becomes soft and 
will smear on the sides and bottom of the container.* The balls 
of paste may then lose their rigidity and tend to flatten out or 
lose their spherical form. This point, which is very sharp, oc- 
curs within narrow limits and is the end point. The apparatus 
required and method of test are given below. 

Burette.—A standardized burette should preferably be used. 
If not standardized, the determinations should always be made 
by starting with the same burette filled to the zero point. In 
this way possible differences due to variations in the burette 
graduation are largely eliminated. 

Container for Mixing Pigment and Oil.—For this purpose 
a smooth, round bottom jelly glass is very well suited. Those 
having dimensions of approximately 214 inches diameter at top, 
and 314 inches deep are easily obtainable. Flat bottom glasses 
or those having fluted sides or bottom should not be used, as the 
pigment and paste tend to collect in the crevices, making ac- 
curate determinations difficult. 

Spatula.—A blunt end, 4 inch, stiff blade spatula should be 
used. If the blade is too limber, excessive stirring is required 
and the results are liable to vary. 

Preparation of Sample.—The sample to be tested should first 
be placed in a suitable container (a small wide-mouth bottle is 
adaptable) and well shaken so as to assure the elimination of 
any packed particles or lumps. This is especially important if 
the pigment has been packed in barrels or otherwise kept in a 
manner that is liable to cause it to pack together. If excessively 
moist, the sample should then be air dried at room temperature. 

Procedure.—Twenty grams of the pigment are placed in the 
glass. The oil is then run in from the burette, either drop by 
drop or with successive small additions. Either of these methods 
will give check results. If the drop method is used the rate of 
flow at the start should be about one drop per second. If the 


* See Fig. 61. 


OIL ABSORPTION OF PIGMENTS 115 


small addition method is used, quantities of 1% cc. should be 
added. As the absorption of the oil increases, the rate of flow 
or quantity of the additions is decreased. This is fully ex- 
plained later. The oil is run in so as to strike the dry pigment 
in the center. As the oil comes in contact with the pigment, the 
dry pigment that has not been wet should be lifted from the 
outer edge and placed over the oil so as to bring all the oil sur- 
face in contact with the pigment. This is best accomplished 
either by lifting it up on the spatula and dumping it off on the 
oil, or very lightly throwing it over the oil. 

When the pigment particles become wet with the oil they tend 
to coalesce and form small lumps of paste. These lumps should 
be kept distributed throughout the mass. This is done by lightly 
stirring the mixture of these paste lumps and dry pigment in 
the manner of stirring described above, being careful not to 
use pressure in the mixing. If the drop method of oil addition 
is used this stirring should be carried on continuously with the 
operation of bringing the dry pigment in contact with the oil 
surface. If the successive addition method is used this stirring 
should be done after each addition. As the absorption of oil 
progresses these lumps of paste, by taking up more pigment 
and matting together, form larger lumps which when stirred 
around form balls. When this point is reached the rate and 
quantity of the oil addition should be very much decreased and 
only a few drops added at a time. In adding the oil at this point 
it should be allowed to strike on these lumps and not on the re- 
maining dry pigment. After each oil addition these lumps are 
lightly stirred around so as to bring the oily surface into con- 
tact with the remaining dry pigment. 

With further oil addition and stirring, these balls will with 
most pigments join together and form one large lump, with but 
little dry pigment remaining. With certain pigments, however, 
the lumps or balls of paste do not join together but remain 
separate and continue to collect more pigment. At this point, 
which is close to the end point, the oil is added very carefully, 
one or two drops at a time. With many pigments one drop is 
sll that is necessary to establish the end point. At this stage, 
the oil should be allowed to strike on the surface of the lump or 
lumps. They should then be worked around so as to pick up 
more of the pigment. When all of the remaining dry pigment 
has been picked up and wet, the end point is reached. This is 


116 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


indicated as above explained by the paste lump becoming much 
softer and easily spread with the spatula. When stirred around 
it smears on the sides and bottom of the glass. This end point 
is very sharp and occurs within narrow limits. With most pig- 
ments only one or two drops of oil is required to change the 
relatively hard dry lumps which do not smear the walls of the 
container into a fairly soft paste which will smear when stirred 
around. If, when the end point is reached, the paste lumps are 
broken down or spread with the spatula, it will be noted that the 
oil is uniformly distributed throughout the mass and no dry pig- 
ment remains. 

Different pigments have certain individual characteristics in 
absorbing oil. These must be given consideration, and it is 
sometimes necessary to slightly modify the procedure in order 
to conform with these peculiarities. For example, some pig- 
ments absorb the oil readily and in a uniform manner, while 
others take up the oil slowly. The paste lumps of some are 
smooth and free from hard agglomerates and are easily kept 
uniformly mixed. Others tend to form hard lumps. With such 
it is difficult to keep the mass uniform. When the end point is 
reached with certain pigments, the paste lumps will be quite 
firm. Other pigments will be firm up to the end point and then 
suddenly become very soft; in some instances of semi-paste con- 
sistency. These differences are largely due to certain surface 
tension relations of the pigment and oil, a discussion of which 
is outside the scope of this paper. A little experience with the 
various pigments will enable the operator to effect such modifica- 
tions as will be necessary to conform with these conditions. 

Close checks can be obtained on the test made in accordance 
with the procedure explained above. Experienced operators 
rarely vary more than 0.1 cc. in check tests or in tests conducted 
by different operators on the same sample. For ordinary pur- 
poses a variation of 0.2 cc. is sufficiently close. A variation of 
more than this amount on check tests can only be considered as 
an error in the operation. In testing new pigments or where a 
close determination is desired, two or more check tests should 
be made. A little experience and a consideration of the follow- 
ing previously stated precautions is sufficient to insure accurate 
results: 


(a) The pigment must not be moist. 


OIL ABSORPTION OF PIGMENTS key 


(b) It should be well shaken before making the test. 

(c) It should not be of a temperature lower than 70° or higher 
than 100° F. 

(d) The oil should be well settled and of a standard acid 
value. 

(e) The oil should not be added too fast, nor should it be 
added slower than is necessary. : 

(f) The mixture should only be stirred enough to keep the 
mass uniform and bring the pigments in contact with the oil. 

(g) Excessive stirring tends to lower the result. 
_ (h) The stirring should be done lightly and care taken not 
to use pressure or endeavor to mix the pigment and oil by this 


means. 
(i) When nearing the end point, the oil should be added 
slowly and in small amounts (one or two drops at a time). 


FIGURE 61 
Pigment Mass Just Before Pigment Mass at Point of Satura- 
Point of Saturation. Mass is tion. Mass Loses Its Spherical Form 
Spherical and Does Not Mark and Smears Glass. 


Glass. ; 


CHAPTER XIII. 


TEXTURE OF PIGMENTS 


The property of many pigments to readily disperse and be- 
come finely divided when mixed with a liquid, even without 
grinding, is due to a quality termed “texture.” This term is 
used to designate the structure of the pigment, and bears no 
relation to its fineness. 

As there has been some confusion among paint manufacturers 
regarding the application of the terms of “texture” and “fine- 
ness,” the following definitions and discussion are given. A 
comparison of them will serve to show their proper application 
and import. 

Fineness.—“Fine. Consisting of minute. particles, grains, 
drops, flakes, ete.” (Century Dictionary.) And its opposite 
characteristic, “Coarse. Coarse-grained, consisting of large 
particles, fibres or constituent elements.” (Century Diction- 
ary.) 

From the above definitions it is apparent that the terms 
“eoarse” and “fine” refer to the extent of the subdivision of the — 
particles constituting a mass. They are quantity terms and are 
subject to the determination ‘of degree of either property by 
measurement of the size of the particles. 

The terms “hard” and “soft? (which are the attributes of 
texture) are quality terms and relate to the character of the 
mass or of the particles of which it consists. They are in this 
sense relative terms and as such are determined in degree by 
comparison and by such means as will indicate differences 
sharply. 

Fineness, then, relates to the degree to which the particles - 
have been subdivided, and texture to the character of the par- 


Texture—“Texture. By extension, the peculiar disposition of the con- 
stituent parts of any body—its make, consistency, etc.; structure in gen- 
eral, as the texture of rocks, the mode of aggregation of the mineral sub- 
stances of which rocks are composed. It relates to the arrangement of 
their parts viewed on a smaller scale than that of their structure. The 
texture of rocks may be compact, earthy, granular, scaly, slaty, etc.” 
(Century Dictionary.) And the attributes of texture: “Hard. Solid and 
firm to the touch; firm in substance and texture, so as not to be readily 
altered in shape, penetrated, or divided; so constituted as to resist com- 
pression, penetrating, dividing or abrading action; opposed to soft.” 


118 


TEXTURE OF PIGMENTS P19 


ticles, independent of their size. As applied to pigments, the 
important properties and the most desirable from a general 
paint-making standpoint are maximum fineness and soft texture, 
although there are certain exceptions to this, such as the use of 
hard pigments in wood fillers and in small amounts in certain 
mixed paints. 

From this it will be seen that pigments of equal fineness may 
differ greatly in texture or of similar texture may vary in their 
degree of fineness. Closely related to the texture of a pigment 
are, ease of grinding, character of finish, settling and hardening 
in the package, and to some extent flowing and spreading of 
the paint. A pigment of soft texture disperses more readily, 
grinds more easily, produces a smoother finish, has less tendency 
to settle and harden, and makes a better flowing and spreading 
paint, than one of hard texture. 

The test described herewith for determining the comparative 
texture of pigments has been widely used by certain manufac- 
turers and found valuable as a method for setting standards and 
in investigation work. It is based on the extent to which pig- 
ments under certain conditions will disperse in a liquid having 
good dispersing properties. The liquid used is a mixture of 
equal parts by volume of blown linseed oil of a specific gravity 
of approximately .945 to .950 and pure turpentine. This mix- 
ture should be of slightly higher viscosity than raw linseed oil. 
If on account of age or storage in open tanks the blown oil has 
become heavy, a further addition of turpentine should be made 
so as to bring the mixture to the proper consistency. It should 
be strained through silk or very fine cloth before use. 

Apparatus Required.—Ground or frosted glass plate about 
one foot square. Several clear glass plates 4” x AUT OYGA x: 6, 
Three-inch glass muller. Artist’s spatula (4” blade). Small 
spatula. 50 cc. beaker. It is important that the small glass 
plates be thoroughly washed with soap and water, and then with 
aleohol so as to remove all dirt and grease from the surface. If 
a soft cloth is used for drying the washed glass, it should be first 
washed in alcohol, and dried, so as to free all loose particles of 
lint. 

Method of Making Determination.—12 cc. of the liquid de- 
eee ee 
(Century Dictionary.) “Soft. Yielding readily to pressure, easily pene- 


trated; impressible; yielding; opposed to hard; easily susceptible of 
change of form.” (Century Dictionary.) 


120 EXAMINATION OF PAINTS. VARNISHES AND COLORS 


scribed are used with from one to two grams of pigment. The 
amount of any pigment used depends on its oil absorption. With 
high oil absorbing pigments such as zinc oxide, high oil absorp- 
tion lithopone, asbestine, china clay, and similar pigments, one 
gram is sufficient. With medium oil absorption pigments, such 
as low oil absorption lithopone, whiting, silica, etc., one and one- 
half grams are used. For pigments of low oil-absorption, such 
as basic carbonate or basic sulphate white lead, barytes, etc., 
two grams are used. As the test is only qualitative and largely 
comparative, a closer calculation than the above, based on oil 
absorption, is not important. 

The pigment is mixed to a thin semi-paste on the ground glass 
plate with about 1 cc. of the liquid. This paste is then well rub- 
bed out with the muller in three mulling operations for one 
minute each. This is done by mulling the paste continually for 
one minute, then scraping it up to a pile on the plate. This 
operation is carried out for the third time. The purpose of this 
mulling is to break down the particle agglomerates of the pig- 
ment and to cause each particle to become wet with the liquid. 
A light pressure in mulling, sufficient to thoroughly rub out the 
paste, is preferable to a heavy grinding pressure. 


It has been found that mulling to the extent stated is sufficient 
to practically eliminate any variation in results, although further 
mulling, even with more pressure, does not materially affect the 
results. Between each mulling operation, a few drops of the 
liquid should be added in order to compensate for evaporation 
or thickening condition. 


After the mulling is completed, thin the paste with a further 
amount of the liquid and transfer to the beaker. Add the bal- 
ance of the liquid, and stir thoroughly. Let stand for one or 
two minutes to eliminate the air. Then pour the mixture on a 
clean glass plate, holding the plate in an almost vertical position 
and pouring the paint across the upper portion so that it will 
flow down. Place the plate in a vertical position so that the 


excess will drain off. It should be left in this position until the 
film is dry. 


In this test the pigment particles of soft texture will become 
so finely divided that they are either colloidally dispersed or so 
finely dispersed as not to be visible to the eye. The harder 
particles which have not been finely dispersed show up. As the 


TEXTURE OF PIGMENTS IRA: 


FIGURE 62 


Photomicrograph of paint of good texture flowed 
on glass. Note fine particles. 


segs 
oat 


Pte Sot 


eres 


FIGURE 638 


Photomicrograph of paint of poor texture flowed 
on glass. Note coarse particles. 


122 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


mixture flows down the plate, the smaller particles remain at 
the top in the thinner part of the film while the larger particles 
as well as pieces of lint and dirt flow down to the lower part of 
the plate and can be easily observed in this portion of the film. 

Interpretation of Results—Some pigments disperse easily and 
to a great extent, while others contain many small and a few 
large particles which do not readily disperse. Others contain a 
majority of large particles. A comparison of different pigments 
or different lots of the same pigment will serve to show their 
character in this respect. 

Liquids also vary in their dispersing property. Some will 
disperse pigments to a greater extent than others. Certain 
liquids may with certain pigments have the opposite effect—that 
of causing some pigment to agglomerate and form large, hard 
particles. This test may therefore be used to determine the 
relative dispersing properties of paint liquids. For this purpose 
any one pigment may be tested with several liquids in the man- 
ner described, and comparisons made. 


CHAPTER XIV. 


TESTING THE LIGHT-RESISTANCE OF LITHOPONE 
EFFECT OF ACIDITY OF VARNISH AND OIL 


The darkening and discoloration of lithopone, due to the ac- 
tion of ultra-violet rays in sunlight, have in the past constituted 
a serious drawback to the use of this pigment in paints and 
enamels. During recent years, however, continued research on 
the part of lithopone manufacturers has resulted in the develop- 
ment of much more light-resistant products, as well as great 
improvement in other qualities. at A ra 

The light-resistance of lithopones has been the subject of 
numerous investigations. There.is much difference of opinion 
among the investigators regarding the nature of the change and 
the causes of it. The present chapter, however, is limited to a 
discussion of methods for testing light-resistance. Other physi- 
cal properties of the samples tested, such as oil absorption, fine- 
ness, livering, etc., are treated elsewhere. 

The comparative light-resistance of different samples is 
readily determined on clear days by exposing them in a suitable 
liquid, on properly mounted panels, to the. sun’s -rays. _Fre- 
quently, however, atmospheric conditions are such that sun tests 
cannot be carried out. Moreover, the intensity of the active rays 
and the relative humidity of the atmosphere varies greatly at 
different times and in different localities. It is therefore high- 
ly desirable to have.an artificial light source from which the 
ultra-violet-radiation can be maintained constant and which has 
actinic effects similar to sunlight. Humidity, temperature, and 
other variable factors should be under COMPO 2) =: i: 

The quartz mercury vapor arc has been ‘extensively used for 
testing the light resistance of paints, pigments, and dyes; and 
is a standardized piece of apparatus.. As a means of making 
eontrol tests in lithopone manufacture, it has been found: very 
practical. More recently the iron are has been’ adapted for this 
purpose. It is believed that the iron arc, when properly con- 
structed and fitted with the necessary devices for regulating and 
controlling the current, will also prove satisfactory in paint and 
varnish plant laboratories for certain types of work. It can 
be readily constructed at a very reasonable cost and produces a 


123 


124 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


light practically constant in the intensity of the ultra-violet radi- 
ation. The chief advantage of the mercury vapor lamp is the 
large area of the light source which permits of the testing of 
large samples or a number of small samples at the same time. 
However, the proportion of ultra-violet rays transmitted through 
the quartz tube of the mercury lamp decreases continuously with 
age (see Scientific Paper No. 330, U. S. Bureau of Standards). 

Before describing the results obtained in our investigation 
with the iron arc, there is presented herewith a paper on the 
testing of lithopone, submitted to the writer by Messrs. Breyer, 
Nelson, and Farber. They point out the usefulness of the quartz 
mercury vapor lamp as against the iron arc, and refer exten- 
sively to the testing of all samples of lithopone in the paint 
liquids in which they are to be applied in the form of paints. 
The information they transmit regarding the effect of high 
versus low acid oils upon the darkening of. lithopone is of ex- 
ceptional importance. 


Inight Resistance Test for Lithopone-—A sample of 
three grams of the lithopone is rubbed down to a stiff 
paste in one part of China wood oil vehicle (a common 
type of China wood oil—rosin combination vehicle con- 
taining lead dryer) and one part naphtha. (Always 
make the test in the vehicle in which the lithopone is to 
be used, or at least in a vehicle of the same type and 
properties as the vehicle to be used.) The mixture of 
oil with thinner is freshly prepared for each set of 
tests. The paste is spread on a porcelain plate or pal- 
ette in a smooth, even layer, at least one inch by three 
inches in area. A standard, or standards, should be 
run with each set of samples, all being prepared in the 
Same manner. Care should be taken that the pastes 
of all samples are approximately of the some consist- 
ency. If paints are tested use the paint as it comes 
from the can. 

The palette is put in a warm place and the pastes 
dried until the glossy surface disappears. (In case the 
testing is done in a vehicle yielding a gloss surface. 
such as a gloss white paint, dry until the surface will 
stand being submerged in water.) A strip of opaque 
black paper or a rule is laid across and above the 
samples to shadow a portion, and the samples are then 
exposed to the ultra-violet light under a thin layer of. 
water 1/32” to 14” deep. (Exposure under water in- 
sures a uniform relative humidity.) A desirable 


LIGHT RESISTANCE OF LITHOPONE 


length of exposure to bring out significant differences 
in lithopones is five minutes at a distance of twelve 
inches from the light, when the current is 4 amperes at 
180 volts across the line. 

Description of Light Used for Testing.—The light 
source found to be most satisfactory for laboratory 
testing is the Standard Uviare Laboratory Outfit, manu- 
factured by the Cooper Hewitt Electric Company, 
shown in Fig. 64. This equipment is furnished for 
either 220 volts direct current or 110 volts alternating 
current. So far it has been considered superior to 


4 

a. 

BN 

d 
ee 
| 
aA 


Detail showing 

: burner holder with 

Uviare Laboratory Outfit. Composite horizontal type 
showing two positions of hood. burner in position. 


FIGURE 64 


125 


126 


EXAMINATION OF PAINTS, VARNISHES AND COLORS 


other forms of equipment for routine tests on account 
of its simplicity of operation, being practically self- 
regulating. . 

The details of the burner and holder are also 
shown. The burner holder is universally adjustable 
in all planes and will take either the vertical or the 
horizontal type of burner. 

The useful life of a quartz burner has been fctina 
by experience to be from 1,000 to 1,500 hours of steady 
operation, and a new burner can easily be substituted. 
In practical laboratory test work this provides an 
amply uniform source of light. A burner in use at the 
time this is written has been used for testing dozens of 


| Ultra Violet Light. — 


FIGURE 65 
(A) Uviare light test on seven Lithopones. Time, 5 minutes. 


LIGHT RESISTANCE OF LITHOPONE 


samples daily for 114 years and is still considered 
useful. 

Also, since in any case all tests are run against a 
standard, the behavior of the standard quickly indicates 
any falling off in the effectiveness of the quartz burner. 


Uviarc Tests Comparable with Sunlight Tests.— 
Experience has already proven that tests carried out in 
the above manner are comparable with sunlight tests, 
and are a true indication of light resistance. This is 
also demonstrated by the photographs in Figs. 65 and 
66. In these tests seven different lithopones of varying 
light resistances have been submitted (a) to ultra-violet 


FIGURE 66 
(B) Sunlight test on seven Lithopones. Time, 2% hours. 


127 


128 


EXAMINATION OF PAINTS, VARNISHES AND COLORS 


ds 


A 
wah 
ae 


fi 


t 
%) 


ai 
a 
i 
ae} 
Vay) 
was 
a 
% 
5 


a 
at 
hs 
: P. iE . 7 
co ones * 
a, 
ei 
Cy as a 
a) 
tak 
Cece 
43 
5 
| Mole 
> ae 
A? 


oo 


t 


light, as described above for five minutes, and (b) to 


bright sunlight for 214 hours (sample under water). 
It will be seen that in each case there is perfect agree- 
ment in the relative light resistance of the lithopones. 

Humidity Must be Controlled During the Test Period. 
—It is a well-known fact, as indicated by the literature 
on actinic effects, that the presence of moisture in- 
creases the rate at which chemical changes are pro- 
moted by ultra-violet radiations. This is true of the 
darkening of lithopones. It is, therefore, very im- 
portant that all comparative tests of this nature be con- 
ducted under known and reproducible humidity condi- 
tions. Since any condition short of complete saturation 
is not easily maintained constant or reproduced with- 
out special equipment, the simple expedient of im- 
mersing the samples in water is the most reliable means 
for eliminating the humidity variable from the test. 

We would also point out that testing under saturated 
moisture conditions has the further advantage that the 
lithopone is being tested under the most trying condi- 
tions it can ever be required to meet in practise. 

Effect of Vehicle on Results of Light Resistance 
Tests.—Under the foregoing description of the test 
method it was also suggested that the vehicle is an im- 
portant factor in the results of light resistance tests 
and that tests on lithopones intended for paint purposes 
should be made in a practical paint vehicle. 

A number of lithopone users have insisted that 
water or glycerol pastes should be used in testing for 
light resistance. From every standpoint this is wrong, 
unless the lithopone is actually to be used in water or 
glycerol vehicles. That such a method is fundamentally 
wrong and misleading is amply demonstrated by the 
tests in Fig. 67. 

In Fig. 67 the original lithopone is rubbed down in 
(1) regular flatting oil test vehicle (2) water and (3) 
glycerol. There is no agreement in the results and, 
obviously, only the test in the oil vehicle can be accepted 
as a criterion for lithopones to be used in oil paints. 

Further, the use of water and glycerol pastes may 
lead to extremely erroneous conclusions about improve- 
ments in the quality of lithopones. Lithopones can 
easily be “doped” so as to vary their light-resisting 
properties. In Fig. 67 the same lithopone has been 
so “doped” and tested in (4) flatting oil vehicle (same 
as above), (5) water and (6) glycerol. It is important 
to note that while this lithopone now shows perfect 
light resistance, in both water and glycerol pastes, 


5 et 


Sr nan LO eS 


ee 


i 
2 


mar 
iin 


> 


ne ee aed eer. 
Se PRE TS ala BR es 
nt F Vey a. a9 > os 


t 


LIGHT RESISTANCE OF LITHOPONE 


TLignt Resistance test. 
Exposeca to Ultra Violet 
Light for five(5)minutes, 


Orignal 
_ -Rubbed in oi] 


4F 


Treated 
Rubbed in oil. 


Treated 
Rubbed in Water, 


FIGURE 67 


Comparison of light resistance tests on the same Litho- 
pone in (1 and 4) oil vehicle (2 and 5), water, and (3 and 


6) glycerol. 


there has been no improvement with the flatting oil 
vehicle. Therefore, it would be a mistake to say that 
the quality of the lithopone had been improved. 
Preferable to Test in Same Oil Vehicle as Used in 
Practise.—The light-resistance properties of lithopones 
are also affected by variations in the properties of the 


129 


130 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


oil vehicles themselves. Fig 68 illustrates how very 
important this factor may be. 


A single lithopone was 


tested in a series of vehicles typical of the principal oil 
products on. the market. 


(In these tests the oils have 


FIGURE 68 
Acid Acid 
No. No. 
1. Raw Linseed Oil. .................... 8. Standard Acid Refined 
2. Improved Raw L. Oil............ 5—7 Linséed O1tl..... 2 eeee 4—6 
3. Alkaline Refined Varnish 9. White Acid Refined Oil... 6.5 
0 5 | MAR ESS git ON eee 12 Pa 3.0 10. Pale Grinding 
4. Alkaline Refined Oil............... 0.5 “11. Boiled On =a 
5. Alkaline Refined Oil Re- 12. Kettle. Bodied 
friverated ico. eee 0.5 13. Blown Bodied Oil .................. 7-10 
6 Alkaline Refined. Oil.............. 3.0 14. Boiled. Oil 22222 5-7 
7. Acid Ref. Oil Refriger- 15. Treated China Wood Oil... 5-6 
po MR ae caeiechiineoat: Ree oe 10 | 


Light Resistance test on a Lithopone in various oil vehicles. 


LIGHT RESISTANCE OF LITHOPONE 


been thinned with volatile so as to dry to a semi-flat 
surface.) Very few of the results check one another. 

If we consider the results further, we find that, gen- 
erally, the important determining factors appear to be 
the acid number of the vehicle, and whether the oils 
are acid or alkaline refined. The presence of acid ma- 
terials apparently increases the light-resisting prop- 
erties. 


FIGURE 69 


Test further illustrating effect of vehicle treatment on 
the light resisting properties of a Lithopone. 


Fig. 69 presents still further evidence that effects 
of changes in the properties of oils, which are brought 
about in the process of manufacturing, must be serious- 
ly considered as factors in choosing the vehicle in which 
to conduct light-resistance tests. 

This effect of increased acidity is also illustrated 
in Figs. 70A and 71B (A) and (B). (A) shows the ef- 
fect of increasing acid numbers from 1.0 to 20.0 in an 


131 


a Mes 0 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Acid Number 1,0 


Acid Number 5,9 


Acid Number 10,0 


cine. ee 


Acid Number L5.0 


Acid Number 20,0 . 


FIGURE 70 A 
70 (A) Alkaline Refined Linseed Oil. 


alkaline refined linseed oil. The acidity was increased 
adding linseed fatty acids. (B) compares a treated 
China wood oil vehicle with a series consisting of in- 
creasingly acid raw China wood oils. Fatty acids of 
China wood oil were added to increase the acidity of 
this vehicle. 

That commercially used flatting vehicles might differ 
very widely in their influence on the light-resistance 
properties of a lithopone, follows as a natural deduc- 
tion, from what has just been said. But this is more 
forcefully demonstrated as an actual fact by the tests 
with two flat wall vehicles illustrated in Fig. 72. 
In this case:vehicle (A) probably is a combination of 
linseed oil with some China wood oil. The acid number 
of this vehicle averages about 13. Vehicle (B) is a 
straight treated China wood oil vehicle having an aver- 
age acid number 5-6. 

All of the tests just presented suggest that certain 
precautions must be accepted as essential in making re- 
liable comparative light-resistance tests on lithopones, 
WAZ: 

(1) Always run the test lithopone sample against a 
standard or standards. — 


LIGHT RESISTANCE OF LITHOPONE 33 


PE: pave. Sale 
| Added Fatty Acids to Raw Ch 
“Wt Leds Reset the, ingrense 
i Ww 
the light resistance... cules 
1 Treated China Wood 


1 
Raw China Wood Oil, A.N.4.0 
G oy 


10, 
is Acid Number 15.8 
5 Acid Number 20.0 


#1 


#2 


FIGURE 71 B 
71 (B) China Wood Oil Vehicle 
Effect of increased acidity of vehicle on light resistance of a Lithopone. 


(2) The humidity conditions must be maintained 
constant if different tests are to be considered at all 
comparable. 

(3) The test vehicle must be of the same type and 
similar in properties to the vehicle used in practise. 

(4) Watch the test vehicle for any variation in 
properties. This refers to variations in acidity, 
especially. 

The results given in the following pages were obtained with 
an iron arc which was designed, in its original form, by Dr. 
A. H. Pfund.* The intensity of the ultra-violet radiation varies 
with the current passing through the arc. It is therefore neces- 
sary that the amount of current be properly adjusted by insert- 
ing a variable resistance in the line. The length of the arc must 
be readily adjustable so that the proper potential across it may 
be maintained. It has been found that the arc constructed as 


* Astro-physical Journal, Vol. 27, p. 296 (1908). 


134 EXAMINATION OF PAINTS. VARNISHES AND COLORS 


“S/li/er, 


FIGURE 72 


Difference in the light resistance of a Lithopone in two commercial flat 
wall vehicles. (A) Probably a combination Linseed Oil-China Wood Oil 
vehicle. Acid Number 13. (B) A treated China Wood Oil vehicle. Acid 
Number 5-6. 


described herein burns best at a current of five amperes with 
a potential of 40 volts between the electrodes. 

H. E. Eastlack and J. E. Booge have done much toward the 
development of a standard light-resistance test. An apparatus 
similar to that constructed by them was used in the present 
work. 

LIGHT-RESISTANCE—IRON-ARC TEST 


Submitted by H. E. Eastlack and J. E. Booge 


a. Principle of Method.—The sample of lithopone in 
the form of a water paste is exposed under a quartz 
cover glass to the action of a standard iron arc, at a 
distance of 10 cm. A portion of the sample is covered 
with opaque material. The time required to produce 
the first appearance of daikening, as indicated by a 


LIGHT RESISTANCE OF LITHOPONE 135 


FIGURE 73 
Diagram of iron arc equipment used in our work. 


faint but definite line of demarkation between the ex- 
posed and unexposed portions of the sample, is taken as 
a measure of the light-resistance of the sample. 

b. Apparatus and Materials Required: 

Iron arc with voltmeter, ammeter and rheostats. 

Sample holder with an optically clear disc of native 
quartz crystal (30 mm. dia. x 1.56 mm. thick) .f 


Comparative tests by three different laboratories (see below) indicates 
that exact adherence to the specifications for the quartz disc is important. 


136 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Spatula—hard rubber, small. 

Beaker, 50 cc., or glass plate for mixing paste. 

Distilled water. 

c. Procedure: 

1. Preparation of Sample—Put 3-5 g. of the litho- 
pone into a 50 cc. beaker (or on a glass plate), and 
about 2 ec. of distilled water, and with a small rubber 
spatula mix the water and lithopone in such proportion 
that a smooth, moderately thin paste is obtained. Place 
a portion of the paste on the back of the quartz dise and 
press a small piece of glass down over the paste to 
prevent its drying out during the test. The surface 
viewed through the quartz disc should be uniform and 
free from air bubbles. Place the plate carrying the 
disc in the sample holder at a distance such that the 
surface of the sample is 10 cm. from the center of the 
arc. Cover a portion of the sample with a strip of thin 
brass or other opaque material. 

2. Starting and Operating the Arc.—Before starting 
the arc see that the upper electrode is fairly free from 
ferric oxide and is adjusted to extend 14” to 32” below 
the radiator and is centered directly above the lower 
electrode. Now close the main switch, bring the elec- 
trodes into contact with each other and quickly separate 
them—thus starting the arc. 

The shallow cup on top of the lower electrode should 
be completely filled with a bead of magnetic oxide. If 
this is not the case, raise the current to about 10 
amperes until the top of the upper electrode is in a 
thoroughly molten condition. By quickly bringing the 
electrodes into contact and then separating them again, 
the drop is transferred to the lower electrode. The 10- 
amp. current is then maintained until the top of the 
upper electrode is again molten, so as to obtain a 
symmetrical bead on the upper electrode also. 

Now cut in resistance until the current is adjusted 
to exactly 5 amperes, using the large rheostat for 
coarse adjustments and the small rheostat for fine ad- 
justments; also adjust the distance between the elec- 
ar cee until the potential between them is exactly 40 
volts. 

3. Exposure of Sample and Interpretation of Re- 
sults——When the arc is operating smoothly at 5 


*In a private communication Pfund and Eastlack state that a somewhat 
steadier arc may be obtained by using a current of 35 volts and 6 amperes. 
This gives about the same wattage and therefore the same intensity of 
light as a current of 40 volts and 5 amperes. 


LIGHT RESISTANCE OF LITHOPONE od 


amperes and 40 volts, open the shutter, exposing the 
sample to the arc, and close it again at the end of 30 
seconds. Examine the sample carefully in a good light 
to see if the exposed portion has been darkened (as in- 
dicated by a line of demarkation between the exposed 
and unexposed portions). If not, another portion of 
the sample is exposed for 60 seconds, or, if the sample 
was appreciably affected in 30 seconds, the next trial is 
made at 15 seconds. For each exposure the position of 
the strip of brass protecting part of the sample must be 
changed. 

Repeat the exposure of the sample to the are (using 
fresh portions of the paste, if necessary) until the 
time required to produce the first appearance of dark- 
ening has been satisfactorily determined. The pre- 
cision which is regarded as satisfactory for exposures 
of different lengths is indicated below: 


Total time for 1st “Eyd-Point” should be 

darkening. located within— 

Ee LON eS eae geese eR eres eer 1 sec. 

SE Nara taeeetnieebbestgereete eee contre EE: Sh 

i TS I Ste pe Neen ee en Pee oer heres! 
Ie eigen se necnctb at itrvenagtencnereatceernatbecesoane Ee eee 
WC PLAT RTNS Shi ee Aa IR na Nee a neces a 20 oe 
NG T OUTING) os 0 2s Sse ae vee eeeunneen aime eee a 


The number of seconds required to produce first 
darkening is recorded as a measure of the light-resist- 
ance of the sample. Samples which show no darkening 
in 300 seconds (5 minutes) may be regarded as “light- 
stable,” although for all practical purposes samples 
which show no darkening in 60 seconds will not be 
appreciably affected by sunlight when used as a pig- 
ment in oil paints. 


Lithopone Samples Examined.—In the work carried out by 
the present writer, four series of samples were tested. They 
are designated as follows: 


Series A: Laboratory samples. A-l, A-2, and A-3 
were originally obtained for specific-gravity work and 
were about four years old. The other samples of this 
series were from two to three years old. None were 
obtained for light-sensitiveness tests. 

Series B: Set of five samples of varying degrees of 
light-sensitiveness obtained from the Bureau of Stand- 
ards which had been sent to the Bureau by Dr. Booge. 

Series C: Standard samples of varying degrees of 
light-sensitiveness sent by Dr. Booge. 


138 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Series D: Samples from factory batches obtained 
direct from the manufacturers. These represented 
current commercial lots. 

Tests on Water Pastes of Lithopones.—As pointed out in 
Kastlack and Booge’s communication, lithopone is far more sen- 
sitive in water paste than in any other vehicle. When exposed 
to the sun’s rays some samples darken perceptibly in a few 
minutes, while all except one of those examined were more or 
less discolored at the end of one hour under prevailing atmos- 
pheric conditions. Darkening under the influence of the iron 
are is sometimes a question of seconds only, while very few 
samples will stand exposure for ten minutes without discolora- 
tion. | 

Results obtained with the iron are on water pastes of the 
twenty-five samples examined are given in Table XVIII. 

In Table XIX are given the results of tests on series C and se- 
ries D upon exposure to the iron are and to sunlight. The sam- 
ples are arranged according to increasing light resistance. The 
table indicates that for water pastes the order of darkening, in 
general, is the same by the two tests. 


TABIE XVIII 
Iron Arce Tests—Water Pastes 


Sample Time for 
No. darkening. 
|. a) NMC 6 seconds 
|.) La aA Pe 20 seconds 
AH Bo aioe icsssvsvstschncntsnstnsegivnasstencentloactndtsbsncansicas ugar ppicekoociees de se et rrr 5 seconds 
|: a ne An TNE EM CMa Se 60-70 seconds 
DoD oaaccincee i sisbasosiveencnsincearncitin spuawuchdeeqpanesdbaecpebeetuladlesee sc baa nee ae ene 4 seconds 
|. | nn COMA RMN ennORGt we 650-700 seconds 
BAT dicncicesccseiesscsscenocasnonustesiossicscosbusei yes syedenedeclencousscsopet sual sult aaa 6 seconds 
BB es cessicconinsscsconeee i lade cele Disa Battal te ee ena alae ee 250-300 seconds 
Lt i) eee emcee: tee Ur MR a unaffected in 1,200 seconds 
BZ ae, eee fosesigsithnonelaael siponenactic ais oacen ete seed ats baile an 150 seconds 
|S an canis Mean ht ll 30 seconds 
Bak sci seeecscsssdlen alent cifbeoothlanng Deca ele otc er rr 16 seconds 
Ba B ccssssncscevssnsonidnss liad san cncopstopsunsaghia bie Seeaspctapuabieic ates isc get i er 4 seconds 
Ons Seen tmenn reac Meaneirar Incr A Taye unaffected in 1,200 seconds 
95, A ie aE RE US eM SE 135 seconds 
0: NINE CHM EAM ee 40 seconds 
CMA cose cdscctcecosesesectscinonls Heats emabls sda cn does hacen cele cll 18 seconds 
On | eer EI Se iON ee 4 seconds 
Do cosets ncasscen.epeecaesonmssive nnessubedueniniossassdlprassistsd Dabo buaestsstactes Riese = err 95 seconds 
| by EE a Pee ere R ce RE 240 seconds 
DB a Ea A aE Se 85 seconds 
| 5 RM SrA IM ta R AP eee AEN 1,200 seconds 
hn ee Onn EINE CROTOMEIOeCME 950 seconds 
o> een CECE COMM eM COTM ere 30 seconds 


| Ey Ape A MIRE EEN Traian TUR EP OMT eS 600 seconds 


LIGHT RESISTANCE OF LITHOPONE 139 


TABLE XI1X—Order of Darkening—Water Pastes of Lithopone 
Slides for Sunlight Tests Prepared According to the Method of Eastlack 


and Booge 
Sunlight tests. Iron arc tests 
ge a a oan Re eee, 
Color after one hour 
Sample. exposure to sunlight. Time for darkening. 
eS ie: Ue e 0 egeee aera Almost black 4 seconds 
OE 8 Goat A ee aa Very dark gray 18 seconds 
1 Tvtey col Saeki: nica er lee en Dark gray 30. seconds 
Ro Dae ae Dark gray 40 seconds 
{Ue Oe eee Yellowish gray 85 seconds 
10 eee Gray 95 seconds 
SRE Soa. le ee sta Yellowish gray 135 seconds 
Poe i ae eee Gray 240 seconds 
sis Beet Gray 600 seconds 
{Ps Ue Pee ee eee Slightly gray 950 seconds 
ye ee ee os Very slightly yellow 1.200 seconds 
CS a ea ae Very slightly yellow Unaffected in 1,200 seconds 


The day on which the sun exposures were made was very 
hot and the sky somewhat hazy but not cloudy at any time dur- 
ing the exposure. | 


The discoloration of samples D-7, D-4, and C-1 in the sun 
tests faded completely in a few hours. The rest remained per- 
manently darkened although D-2, D-6, and C-3 faded out to a 
considerable extent. 


Tests on Glycerine Pastes of Lithopones.—Lithopone will also 
darken when glycerine is used in place of water in making the 
paste. The time required for darkening 1s somewhat greater 
than for water pastes. Table XX gives the resuits obtained on 
the samples of Series C. 


TABLE XX—Iron Arc Tests on Glycerine Pastes 


Sg A ae rr Unaffected in 1,800 seconds 
gn egies Darkened in 720 seconds 
ie i ene ne Darkened in 120 seconds 
(Od VSS a SENN nO ee Darkened in 45 seconds 
Te ee EI ae crs ee eee oe a Darkened in 12 seconds 


Tests on Varnish Vehicle Pastes of Lithopones.—Some manu- 
facturers and users of lithopone rightly prefer to make the test 
in oil or varnish vehicles in order to more nearly approximate 
actual service conditions. 


Tests were made by us to determine whether the results ob- 
tained in water pastes would run parallel with the results of 


140 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


sun tests on pastes in oil or varnish vehicles. For this purpose 
Dammar Varnish and also a commercial flat wall paint liquid 
were used. The tests were made on eight representative samples 
which darkened when exposed to the iron are, in varying periods 
of time. The results of these tests are given in Table XXI. 

It will be observed that the order of light stability shown in 
this table agrees well with that of Table XIX. Since there is no 
sharp point or narrow limit of time in which darkening can be 
said to occur in the sun tests, and moreover, the color of the 
discoloration varies considerably with different samples, slight 
discrepancies are to be expected. 

Iifforts were made to check the sun tests on Dammar varnish 
and' flat wall paint liquid pastes with iron are tests. The time 
required for darkening in these liquids is, however, so great as 
to make the iron are rather impractical for these pastes. The 
results obtained are given in Table XXIII. 


TABLE XXI—Sun Tests on Dammar Varnish Pastes 


| ee a 
Sample. 2 Hours. 5 Hours. 12 Hours. 20 Hours. 
Data. 
D-1 Unaffected | Unaffected | Very slightly; Bluish gray C-5 
darkened darkest 
bluish gray 
D-2 Unaffected | Unaffected | Unaffected Apparently || C-4 
unaffected 
D-3 Unaffected | Unaffected | Very faintly | Gray D-6 
darkened 
D-6 Unaffected | Slightly Somewhat Quite gray C-3 
affected darkened 
C-2 Unaffected | Unaffected | Faintly Slightly D-1 
darkened bluish gray _Binish gray | 
C-3 Very slight | Slightly Somewhat | Quite gray D-3 
indication darkened darkened 
C-4 Very slightly; Somewhat | Dark gray Vee dark C-2 
darkened darkened gray 
G-5 Slightly Very dark Bluish black} Bluish black|} D-2 | eet 
darkened gray lightest 


LIGHT RESISTANCE OF LITHOPONE 141 


TABLE XXII—Sun Tests on Flat Wall Paint Liquid Pastes 


Final Order 
Sample. 2 Hours. 5 Hours. 12 Hours. 20 Hours. of 
darkening. 
D-1 Unaffected | Unaffected | Very faintly | Somewhat C-5 
darkened darkened | darkest 
yellowish 
| gray 
D-2 Unaffected | Unaffected | Unaffected | Apparently C-4 
unaffected 
D-3 Unaffected | Unaffected | Slightly Slightly D-6 
. yellow 
D-6 Unaffected | Unaffected | Faintly Quite yellow; D-1 
darkened 
C—2 Unaffected | Unaffected | Faintly Slightly C-2 
darkened yellow 
C-3 Unaffected | Unaffected | Apparently | Very light D-3 
unaffected | gray 
C-4 Unaffected |Unaffected |Very slightly | Yellow C-2 
darkened | 
C-5 Very slightly; Very dark | Very dark | Almost black) D-2 
darkened brown brown lightest 


TaBLE XXIII—Ivron Arc Tests on Paint Liquid Pastes 
Time required for darkening Time required for darkening in 


Sample. in Dammar varnish paste. flat wall paint liquid paste. 
Gio P eee oe Unaffected in 3,600 seconds Unaffected in 3,600 seconds 
Ce oa etl Darkened in 500 seconds Darkened in 1,400 seconds 
11 oS a See Unaffected in 3,600 seconds Unaffected in 3,600 seconds 
1B Seon eee ee Darkened in 3,600 seconds Unaffected in 3,600 seconds 


Comparison of results obtained in different laboratories.— 
Light stability tests were made on the samples of series B and 
series C in water paste. Similar tests were also made by East- 
lack and Booge, and at the Bureau of Standards. Results ob- 
tained in the three laboratories are given in Table XXIV for the 
sake of comparison. 

The apparatus used by the writer and by Eastlack and Booge 
are described above. The following description of the apparatus 
used at the Bureau of Standards was submitted by Dr. J. G. 
Thompson, who made the tests, the results of which are given 
in Table XXIV. 


EXAMINATION OF PAINTS, VARNISHES AND COLORS 


142 


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LIGHT RESISTANCE OF LITHOPONE 143 


The source of ultra-violet light was a small iron are 
operating at 5 amperes and 40 volts. The electrodes 
were ordinary soft-iron rods. The dry samples were 
rubbed up to moderately thick pastes with water, using 
a rubber spatula. The paste was spread on one side of a 
plate of crystalline quartz approximately 1 inch x 214 
inches x 1/4, inch thick. The quartz plate was mounted 
in a holder so that the ultra-violet light must pass 
through the quartz to reach the paste, the quartz-paste 
surface being 10 cm. distant from the center of the arc. 
The remote surface of the paste was coverd with a 
glass microscope slide to prevent too rapid evaporation 
of the water. 

The results reported are average values based on 
more than one determination. 


The cause for the discrepancies is not yet apparent, but is 
probably due partly to errors of observation in judging the time 
required for first darkening. Some operators can detect fainter 
shades of darkening than others. EHastlack and Booge have 
found that the composition of different types of iron rods form- 
ing the elctrodes has only a slight influence on the results. 
Probably the greatest source of error arises from the fact that 
different pieces of quartz used vary in their transparency to 
ultra-violet light. : 

According to Luckiesh* crystalline and fused quartz differ 
considerably, the crystalline variety usually being transparent 
further into the ultra-violet region than the fused. Different 
crystals also vary considerably in transparency. The writers 
used a disc of fused quartz one inch in diameter and one-eighth 
inch thick. In order to determine whether the particular piece 
of quartz used would affect the results to an appreciable extent, 
the writers borrowed the piece which had been used at the 
Bureau, using it in connection with their arc. The results 
checked those of Thompson’s quite closely as shown in Table 
XXV. The lower values obtained by Eastlack and Booge are no 
doubt due to their use of an optically clear quartz disc of only 
1.5 mm. thickness. 


* Jltra-violet Radiation, page 73 (1922). 


144 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


TABLE XX V—Results Obtained at Two Laboratories Using the Same 
Quartz Glass 


Institute of Paint and Var- 


Sample. Bureau of Standards. nish Reteeees 
No. 2 Darkens in 80-90 seconds Darkens in 85 seconds 
No. 3 Darkens in 30-85" Saree | Darkens in 30 seconds 
No. 4 Darkens in 16 seconds Darkens in 14 seconds 
No. 5 Darkens in 4 seconds Darkens in 4 seconds 


The following comments were made by one observer to whom 
this paper was submitted: 7 


Apparently temperature plays an important part in 
the color changes that take place when lithopone is ex- 
posed to sunlight or to ultra-violet light from labora- 
tory lamps. It is considered that with rise of tempera- 
ture to a certain extent, lithopone becomes less sensi- 
tive to change. Undoubtedly the condition of the at- 
mosphere in which the tests are made has something 
to do with the effects. It has been found, for instance, 
that darkening is much more rapid in a hydrogen at- 
mosphere than in ordinary air. Tests, however, in- 
dicate that darkening will not take place in an atmos- 
phere of ozone, and in most cases will not take place in 
oxygen. One investigator some time ago rubbed up a 
sample of lithopone in water on a glass slide, and placed 
it in a Uviol tube having a 2-hole rubber stopper, 
through which moist hydrogen was bubbled. The slide 
was exposed to the light of a Macbeth printing lamp, 
specially cored carbon rods being used. It was found, 
for instance, that even zine oxide would darken under 
these conditions, as well as certain copper salts, and the 
result was attributed to a reducing action. 

It has been known for a long time that lithopone 
may be made sunproof when ground in water paste, by 
the addition of small amounts of salts, such, for in- 
stance, aS ammonium, phosphate. However, when the 
same mixture is dried and mixed with oils and exposed, 
it is apt to darken very rapidly. 


In commenting upon the tests outlined in this paper, another 
well-known investigator gave the following information: 


LIGHT RESISTANCE OF LITHOPONE 145 


Sunlight Test—We keep the samples moist by put- 
ting the glass slides on a piece of common blotting 
paper, kept moist by a small glass jar filled with water, 
and a cotton wick leads from the glass jar and is laid 
upon top of the blotter. In this way we have found 
we could keep samples moist for two or three hours, 
which is sufficient to get a good sun test. 

We have found that glass once used will absorb 
energy from the sunlight, and if this same glass is 
used for a second test the lithopone, if it is very sensi- 
tive to light, will turn without being exposed to the sun- 
light. We therefore make it a point to use new glasses 
for sun tests all the time. Using a glass which has al- 
ready been exposed might make a lithophone turn in 15 
minutes as bad as it otherwise would in 30 minutes, and 
thereby give you a wrong test. 

Comparison with Paint-Out Tests.—We have found 
the humidity is the main factor in making lithopone 
paints turn in sunlight. We have made hundreds of ex- 
periments with flat wall paints and gloss paints, and 
find the flat paints to turn much quicker than gloss, 
and if the humidity is below 60 per cent the modern 
lithopones will not turn at all, while the old lithopones 
will turn as black as coal. These tests are made on 
pine boards painted with regular flat or gloss paint, 
one-half covered with paper, the other half exposed to 
the sunlight on the south side of our laboratory. 

Conclusion.—We agree with you, the sunlight test 
and the ultra-violet light test give concordant results, 
and we also agree with you that the ultra-violet test 
will make a quicker test than the sun test. We have 
found, as you did, water to be the best liquid for sun 
test exposure. Whenever a long exposure test 1S 
wanted, the quartz test apparently is the best, as it 
can be used continuously for three or four hours. We 
have noticed, as you have, that the action decreases as 
the tube gets old, and we therefore always carry an 
extra quartz tube in our laboratory for emergency, 
and check tests. As soon as we find the tube in use 
going off, we send it back and have it pumped out, and 
in that way we have had no difficulty in getting ac- 
curate and quick results. 


Conclusions.—The light resistance of lithopone may be tested 
by exposure either to sunlight or to an artificial source of ultra- 
violet light. Tests made on a number of samples indicate that 
the two methods yield concordant results. While the order of 
darkening of a series of pigments is the same by the two 


146 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


methods, a considerably longer time is required for the sun 
tests. 

For research work where there is trained personnel, the iron 
are could be a supplementary part of the laboratory equipment, 
since the intensity of the ultra-violet radiation can be main- 
tained most constant over a long period of time. For this rea- 
son, the iron are could be used to occasionally check up the in- 
tensity of the quartz tube mercury vapor lamp. In other words, 
it could be used as a standardization instrument. 

For ordinary paint factory use, it is suggested that lithopone 
be tested in the liquid in which it is to be used in practice. For 
this purpose, a quartz tube, mercury vapor lamp is most use- 
ful, because several samples of lithopone in different paint 
liquids can be exposed at the same time. In five minutes re- 
sults may be obtained and a photographic record made. 


ADDENDA 


EFFECT OF ULTRA-VIOLET LIGHT ON PIGMENTS OTHER THAN 
LITHOPONE 


The property of darkening when exposed to ultra-violet light 
is shown to some slight extent by other pigments than litho- 
pone; in fact, even by some inert pigments. While several pig- 
ments examined, notably antimony oxide, showed a change, the 
effect is usually only a slight graying which is not greatly ac- 
centuated by continued exposure to the light. While lithopone 
darkens most quickly in water paste, all other white pigments 
examined, if they changed at all, were most readily affected in 
glycerin paste. Results of tests on white pigments other than 
lithopone are given in Table XXVI. It was indicated by study 
of several samples that the presence of small quantities of water 
soluble salts or the effect of certain methods of heat treatment 
were accelerators of darkening. 


TABLE XXVI—Iron Arc Tests on White Pigments Other Than Lithopone 
The term “darkening” refers to a slight “graying.” 


Sample. Water paste. Glycerin paste. 
Zine: Oxide: ic ee aes Unaffected Darkened 
Basic Carbonate White Lead............... Unaffected Darkened 
Basic Sulphat White Lead No. 1..... Unaffected Unaffected 
Basic Sulphate White Lead No. 2...... Darkened Darkened 
TitanOR is ee ee ote Darkened Darkened 
Antimony) Oxide 220.0 Unaffected Darkened 
Bary tess n.cnduaeuhena a eae eee Unaffected Unaffected 
Siena ist oe a eee Unaffected Unaffected 
Zirconium Oxide (Hydrated).............. Unaffected Unaffected 


Ghine) Clay: :i.4.cb- ce seas Unaffected Darkened 


LIGHT RESISTANCE OF LITHOPONE 147 


Results on some colored pigments are given in Table XXVII. 
It is interesting to note that pigments high in lead oxide are ap- 
parently more subject to ultra-violet light effects than some 
others. For instance, dry litharge, even when placed in a glass 
bottle, will show on the surface some color change when exposed 
to diffused daylight in a laboratory over a long period of time. 


TABLE XXVII—Iron Arc Tests on Colored Pigments 


Sample. Water pastes. 
QRPSV ET ETE ey EGS SYST: 9 od Ly Pa a eceneeaneenrereED Unaffected in 1,800 seconds 
Iron Oxide........... I Ee ee ener Unaffected in 1,800 seconds 
CP eC LOW (CED ASIG ) oes ntsstinthnecseccenteenne Darkened in 1,500 seconds 
jee FS ke SS et OG eee een Darkened in 45 seconds 
Light Chrome Yellow (Neutral)................. Unaffected in 1,800 seconds 
2g al SEES WESSON Te SOeE ere ne ee ce Unaffected in 1,800 seconds 
(ey CECI TS eee etc De pe a eee rem Unaffected in 1,800 seconds 
PRES eT aff cee cot Sig te ee 22 ea nano nee aceon Unaffected in 1,800 seconds 
BriiantiOranees ake te ceeteettiee Darkened in 1,800 seconds 
Cirameny CllOw Cran ee oi eee Darkened in 1,800 seconds 
es Speen palo Oe maton) 8 yy Se, See se laren ene Faded somewhat in 1,800 seconds 
PEGE a re LENSE 1 oa ee ere Unaffected in 1,800 seconds 
Vie CURE ARS cs oe Sie Oe OR ea ce a errr Unaffected in 1,800 seconds 


OPACITY OF PIGMENTS TO ULTRAVIOLET LIGHT 


Considerable work has been done by P. R. Croll and J. D. 
Jenkins, on the relative transparent nature of films to ultraviolet 
rays. The writer submitted to them early in 1924 a sample of a 
special glass that had been ground to a pigment, with the request 
that determination be made of its opaqueness to ultraviolet rays. 
Their photographs were made through a thin layer of metallic 
silver which is transparent only in a narrow band of the ultra- 
violet, around 3100A’s. Subsequently they received a Corning 
filter quite opaque to visible rays but very transparent to the ul- 
traviolet down to about 3000A’s. In their subsequent work on the 
glass pigment forwarded to them, they used as a light source an 
iron arc with 5 amperes and 40 volts. Exposure was made in 
back of a screen, at a distance of about fifteen inches from the 
arc, the screen being interposed between the are and the paper. 
The pigments were illuminated by the light from the iron arc, the 
light passing through the screen. They were then photographed 
by means of a pin-hole camera from above. A sketch of the ap- 
paratus used, together with the results obtained with zinc oxide, 
the special powdered glass, silica, and white lead, are shown 
below. 

As was expected, the zinc oxide appeared black in ultraviolet 
light, because such light is absorbed by this pigment. The pig- 
ments that did not absorb the ultraviolet light appeared white. 


148 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Cartehocmclemevtenonesevan.onen pontacnsenansoneah 


as Sad 


amas Cee 


we cee tooneres 


FIGURE 74 


Diagram showing method of photographing pigments by re- 
flected ultraviolet light. (Croll.) 


FIGURE AD 


Photographs of pigments taken by reflected ultra- 
violet light (Croll \ 


CHAPTER XV. 


VISCOSITY OF VARNISHES 
GARDNER-HOLDT APPARATUS 


In making routine consistency determinations where great 
accuracy is not a prime consideration, the simplest and most 
rapid method is preferable. The widely used air-bubble test, 
if used with certain precautions, gives a comparative measure 
of consistency and is sufficiently accurate for most routine work. 
It is common practice, for instance, to compare a sample of 
varnish drawn from each individual batch with a _ standard 
sample of the same varnish which has previously been found in 
actual use to have the desired consistency. To make such a test, 
a small tube or vial is filled with the varnish! and an air space 
is left between: the surface and the cork. When the tube is in- 
verted, the air bubble rises through the liquid at a definite rate, 
depending upon its consistency. The size of the bubble and the 
diameter of the tube are factors which also affect the rate of 
vise. The speed with which the bubble rises through the liquid 
is compared with the rate of rise in a standard sample. This 
test as usually made, however, is only comparative and does 
not give a definite numerical value that may be preserved for 
future reference. 

The writer and P. C. Holdt have recently devised a simple 
type of apparatus that will probably be of service to the varnish 
superintendent and chemist. This apparatus, which is shown 
in the illustration below, consists of a case which holds twenty 
viscosity tubes filled with a series of mineral oils that will not 
show any change of viscosity with time. The tubes are placed 
in alphabetical order. The case also contains a card showing 
the approximate absolute viscosity of the liquid contained in 
each tube. Thus a varnish matching tube E would have a vis- 
cosity of 1.25 poises. It may be preferable, however, for the 
varnish maker always to refer to consistency E or consistency 
H, and so on. With the above type of apparatus available for 
comparison of varnishes, the use of such terms could be re- 
ferred to in correspondence and be specifically understood by the 
operating heads of varnish departments in plants located at 
widely separated points. | 


149 


FIGURE 76 
Gardner-Holdt Viscometer. 


VISCOSITY OF VARNISHES 151 


In this set of viscosity tubes, the difference between any two 
adjacent tubes is equal to about 1% bubble. It may be found 
convenient to reduce the number of tubes to 10, making a dif- 
ference of a whole bubble between adjacent tubes. Following 
are the approximate absolute viscosities of the 20-tube set: 


TABLE XXVIII—Approximate Absolute Viscosity in Poises at 25° C. 


eee Le ae CODE = tp 7 a aE ee 1.40 Ke Pease IP eaeenedee 4.00 
Tee ee CD ote Cece th et 1.65 Lie eee 3.00 Le aoa ities 4.35 
ele hee hon! ABLE) ot 32 Bytes 2.00 Nigsse. 3.20 Ae So eae 4.70 
1a Me eee TULL ho) areas 2.20 IN staat 3.40 Rees 5.00 
| eke dee oho Vga 4 ea eee Det Con sete 3.70 J RES Ta tree 5.50 


A similar set of viscosity tubes could be made up by anyone 
without reference to absolute viscosity. By blending two min- 
eral oils, one of high and one of low viscosity, in various pro- 
portions, a set of standards covering the range of consistencies 
found in any manufacturer’s products is readily made. The 
different tubes could be lettered or numbered or designated in 
any other convenient way. 

Three factors were considered in making up the apparatus 
described above (1) Tubes, (2) Standard liquids, and (8) Con- 
ditions influencing the test. These factors are discussed be- 
low. . 

Tubes.—Various kinds of tubes are now in use for the air- 
bubble test. These tubes vary from the ordinary small homeo- 
pathic vial to specially made tubes, including carbon tubes with 
marks for fixing the size of the bubble. The proper length of 
such tubes is generally determined by the convenience of 
handling. It is important, however, ‘that the diameters of the 
tubes containing the liquids to be compared are practically equal. 
Every tube selected for a case is first carefully calibrated and 
tested in comparison with a standard set of tubes which have 
the desired dimensions. | 

Since the allowable variation in the diameter of tubes is 
very small (not more than 0.1 millimeter), they must be 
accurately measured if direct measurement is resorted to in 
selection. The writer has been unable to secure a gauge suit- 
able for measuring the inside diameter. It has been found, 
however, that if tubes having the same outside diameter as 
measured with a micrometer caliper were used for the bubble 
test with the same liquid they would be suitable for further 
examination and checking with liquids. In several gross of a 


baz EXAMINATION OF PAINTS, VARNISHES AND COLORS 


particular type of tube examined the outside diameter of a con- 
siderable number was found to be 13.35 mm. (+0.1 mm.). All 
were 110 mm. long. This size was tentatively selected as the 
standard size. These are made up at a glass factory from speci- 
ally selected tubing. Out of a gross, not over 20 are usually 
found that may be used as standards. 

Standard Liquids——Since all varnishes change more or less 
with time, liquids which do not change should be selected as 
standards. Glycerin-water mixtures and sugar solutions have 
often been suggested as standards. In both of these there may 
be in certain ranges of concentration very great differences in 
viscosity for slight differences in composition. This result 
necessitates an absolute viscosity measurement for each stand- 
ard liquid. There is, furthermore, in the case of sugar solutions 
the probability of considerable viscosity changes with time, due 
to changes in composition (inversion, fermentation, etc.). The 
requirements of a standard viscosity liquid are, therefore, non- 
change with time and availability over the desired range of 
viscosities. After experimentation, it has been found that satis- 
factory liquids may be made from lubricating oils of known 
types. Compounded lubricating oils, however, cannot be used, 
since they contain vegetable oils, and the free fatty acids con- 
tained in such oils would cause considerable change in the viscos- 
ity of the standards. On the other hand, pure mineral oils can 
be blended to secure any viscosity met with in varnishes, and 
can be kept indefinitely without change. Moreover, they have 
the further advantage that the viscosity of certain intermediate 
blends can be calculated with considerable accuracy. Hence it is 
only necessary to measure the viscosity of a few of the liquids 
in any series of blends. 

Conditions.—The air-bubble test is very susceptible to tem- 
perature. Merely holding a tube of varnish in the hand a few 
moments is sufficient to cause a very appreciable change in the 
viscosity of the varnish. Precautions must, therefore, be taken 
to insure a uniform temperature in the standards and the test 
sample during observation. Lubricating oils and varnishes may 
undergo very different changes in viscosity with equal changes 
in temperature; hence it is necessary to use approximately the 
same temperature in all tests, allowing a variation of not more 
than 2 or 3 degrees either way. The size of the bubble slightly 


VISCOSITY OF VARNISHES 153 


affects the speed with which it rises, and it should be approxi- 
mately the same as that of; the air bubble in the standard 
tubes. 

Results—In a large number of samples of all types of com- 
mercial varnishes recently examined, viscosities ranging from 
0.6 to 5.5 poises at 25° C. were found when working with the 
Bingham plastometer.* To cover the complete range of viscos- 
ities noted above, about fifty tubes would be necessary to include 
differences of 0.1 poise, which is the limit of difference the air 
bubble test will show. It was found, however, that twenty 
tubes are sufficient for all practical purposes, one tube being 
used to represent about each one-fourth poise. For routine 
factory work, ten tubes showing a difference of one bubble be- 
tween adjacent tubes, will probably be satisfactory. In the tubes 
referred to above, the viscosity of the straight oils and of five 
blends were determined experimentally, the absolute viscosities 
of the other blends being calculated. With these, however, the 
approximate absolute viscosity of any varnish can be very 
quickly noted and recorded as a definite numerical value. 

In Scientific Section Circular No. 127, in which a description 
of all types of viscometers in presented, are given the absolute 
viscosities of a number of varnishes as measured in the plasto- 
meter. The absolute viscosities of the standard viscosity liquids 
herein described were measured in the same instrument. If the 
approximate estimation of absolute viscosity by this test is justi- 
fiable, the above varnishes should check with the standard. tube 
which has been assigned the same viscosity. This has been 
found true. The above sets of bubble tubes as made and stand- 
ardized at the writer’s laboratory are now in wide use through- 
out the American varnish industry, being used in place of the 
cumbersome and time-consuming apparatus formerly applied 
for such work. 


* See Circular No. 127 of the Scientific Section. 


CHAPTER XVI. 


SURFACE TENSION AND INTERFACIAL TENSION OF 
VARNISHES AND PAINT LIQUIDS 


While viscosity probably exerts a predominant influence on 
the working and spreading characteristics of a varnish or paint 
liquid, the appearance of the film after application will also 
depend to a certain extent upon the surface tension relations 
existing between the liquid film and the solid underface. Phe- 
nomena such as the tendency of oils to draw together in drops, 
the ease of wetting and grinding of various pigments with 
different oils, etc., have been conceived of as surface tension 
effects. The pitting of varnishes and baking japans or paints 
may also be at least partly due to this cause. 

Surface tension as usually discussed refers to a tension or 
strain at the surface of a liquid in contact with air which causes 
the surface to act as though it were an elastic membrane. In 
a mass of liquid each molecule exerts an attractive force upon 
other molecules within a definite radius. As each molecule with- 
in the mass of the liquid is surrounded by other molecules, 
the attractive forces exerted upon it by surrounding molecules 
is equal in all directions. The molecules immediately upon the 
surface, however, are exposed to molecular attraction only from 
the interior of the mass of liquid and there is consequently a 
molecular pull toward the interior of the liquid. The inward 
molecular pull results in a tendency to contract, drawing the 
surface molecules inward. 

While the measurement of this contractile tension at the air- 
liquid surface is of great theoretical interest and has numerous 
important applications (as for example, the determination of 
molecular weights, structure of compounds, arrangement of 
molecules in the mass, etc.) it has so far been of little assistance 
in solving the problems confronting the paint and varnish chem- 
ist. It does not serve to distinguish between liquids of the same 
class or to explain phenomena frequently observed. Difference 
in the density of the phases on opposite sides of the surface are 
so large as to obscure small differences in the tension of different 
liquids. Conditions existing at liquid-solid or liquid-liquid sur- 
faces, are, however, of great importance in the present con- 

154 


SURFACE TENSION 155 


ee OS 


nection. At such a surface where the density on each side is 
approximately the same, differences in the intensity of the ten- 
sion of different liquids against another immiscible liquid or a 
solid may be detected, since here the combined effects of both 
liquids are measured. The tension existing at other than air- 
liquid surfaces is usually distinguished as interfacial tension 
and will be so designated in this chapter. 

In varnishes (colloidal solutions) and paints (suspensions) 
where the surfaces between solid and liquid are extraordinarily 
great, the magnitude of the interfacial tension between the 
phases becomes a very important factor in determining the char- 
acteristics of the liquid. 

There are, therefore, several kinds of surfaces to consider 
and it is desirable to ascertain whether there is any relation 
existing between the tensions at these surfaces in different 
liquids, and the characteristics of the liquid film. From a prac- 
tical point of view, the most important of these various tensions 
is that at a liquid-solid surface. Very little is known concern- 
ing this tension, and it appears at present impossible to measure 
it. Relative values for the interfacial tension between im- 
miscible liquids can be easily obtained. The absolute methods 
of precision which are at present. available, however, apply to 
only one of the tensions—namely, that in the surface of the 
liquid against air, or its own vapor. 


AIR-LIQUID TENSION 

Three methods are commonly used for measuring the con- 
tractile tendency existing at the surface of a liquid in contact 
with air. 

Capillary tube method.—Surface tension is measured by the 
height to which the liquid will rise in a capillary tube of known 
diameter. The liquid rises until the tendency of the film to con- 
tract is balanced by the weight of the column of liquid. 

Drop weight method.—Surface tension 1s measured by the 
weight of a drop forming at an orifice of known diameter. The 
weight of the drop increases until it overcomes the surface ten- 
sion of the liquid. . 

Air bubble method.—Surface tension ig measured by the size 
of an air bubble forced through the liquid, the size being propor- 
tional to the surface tension of the liquid. 

These methods yield accurate results but require considerable 


156 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


time and manipulative skill. The apparatus illustrated and de- 
scribed herein is easily and quickly operated and yields results 
that check fairly close with the above methods. It was used 
for obtaining the figures given in Table XXINX. 

As indicated in Table X XIX, surface tensions of liquids of dif- 
ferent types, such as oils and volatile thinners, vary somewhat, 
but in different liquids of the same type the difference is too 
small to explain great differences in behavior. It also appears 
that liquids of different types may show the same surface tension 
when they would be expected to have widely varying values. 
The measurement of surface tension, is, therefore, of little as- 


FIGURE 77 


This apparatus, designed by Dr. P. L. DuNouy of the Rockefeller 
Medical Institute, is manufactured by Central Scientific Company, Chicago, 
Nl. For a description of the instrument and details of operation see 
Bulletin No. 82, Central Scientific Company, and the Journal of General 
Physiology, May 20, 1910, Vol. 1, No. 5. 


SURFACE TENSION 157 


sistance in studying the physical pecularities and variations in 
properties so frequently encountered in paints and oils. 


TaBLE XXIX—Measurement of Surface Tension Against Air by DuNouy 


Apparatus 
Orls— Dynes per cm. 
DT a i a hate atten hecerceneetnttenttnneenennencnae 88.5 
heated to 250° C. for 10 mins... eee nent 88.5 
heated to 250° C. for 20 miMS...... ee : 38.5 
heated to 250° C. for 380 Mims... ee 38.5 
heated to 250° C. for 60 MINS... 39.0 
heated to 305° C. for 30 MIMS... ee te 39.0 
Bh AT se sa anaes escent stncnncncnnreteceecnnntntnn a Say bs: 
ara cancectecee nr eneecanh sp cgemsteecenetene ne tneasdecertnetiatmnresertenente 39.0 
Thinners— 
i 6 CSu aC BE a Nera 31.5 
Orthodichlorbenzol SE SN ie ae ameter eer 40.5 
Mineral Spirts— 
Panes aa ee cect eecnenmentedentenegrerenpeonencnenstntnnnenie 29.0 
TN ey sch icles cc cepa een cot eee Ges ee teen, ete 29.0 
Fe aa acl cent ee tbe nencecngePesentennctebennencenntorernnncncnenesons 29.5 
Fe pest cenatenceesenqncnecereceeentttermeneceeeectuneernemnenneneemereagin 29.5 
Br a ecg lnesttR cemececehagreeeeensnatentennecetenenerteesnnnctics 30.0 
ee ae ccd cnet che con danndetenteevonsentennpenndcap metennennnnnnrcnensy 30.5 
Fe accra nel at cen tecne ete tteeneeetbntnnncteentgeenanncetcs 31.0 
Fa accesses epeemepcenersteceprntpesercenttcenepengeeesncnciet 31.5 


Since no way of measuring the tension at a liquid-solid sur- 
face is known, it is desirable that means be found for determin- 
ing values which will explain differences observed in different 
liquids. 

Wells and Southcombe* have observed a definite relation be- 
tween the interfacial (oil-water) tension of lubricating oils and 
their power to wet metallic surfaces. They find that the lower 
this constant is, the greater will be the wetting power or 
“oiliness” of the oil. The ability of various oils to wet a given 
pigment is probably governed by the same relation. If the ten- 
sion is low the oil should spread easily and be readily made to 
cover every facet of the pigment particles. 


INTERFACIAL TENSION 


Relative values for the interfacial tension between liquids 
were obtained by the use of the apparatus shown ato in tig: 
78. This apparatus as prepared by the writer consists of a 5 
ec. pipette bent upward at the lower end and drawn to a point 
having an orifice of about .8 mm. It is supplied with a rubber 


* Soc, Chem. Ind., pp. 51-60 T. (1920). 


158 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


tube and clamp to facilitate filling and to regulate the influx of 
air during the determination. The volume between upper and 
lower marks equal about 4 cc. The figures given in Table XXX 
were obtained with this instrument. The pipette is filled to the 
mark and maintained at this level by closing the clamp. The 
lower end is immersed in a beaker containing water or some 
other immiscible liquid at the desired temperature. Enough air 
is admitted by loosening the clamp to cause a slow efflux of oil 
in a Series of distinct drops from the capillary tip. As the drops 
break loose and rise to the surface one at a time they are 
counted. From 5 to 10 minutes are required for a determina- 
tion. 

The instrument shown at A has been designed by the writers 
to secure greater convenience in operation and greater accuracy, 
and will be used in future work. The size of the capillary to be 


FIGURE 78 


SURFACE TENSION 159 


used will depend upon the viscosity of the liquids tested. It may 
be advisable to have two instruments fitted with different-sized 
capillaries to take care of extremes of viscosity.* 

If a capillary tube as shown at A is used it is essential that, 

in each determination, the top of the tube be perfectly clean and 
free from the liquid the interfacial tension of which is to be 
measured. If it is not kept clean the liquid in emerging will 
spread over the top of the tube, producing drops of non-uniform 
size and render the determination worthless. 
The number of drops formed by a definite volume of liquid is 
inversely proportional to the interfacial tension. In comparing 
two liquids specific gravity must be taken into consideration. 
The number is also influenced by both temperature and the depth 
of immersion of the capillary tip. Since observations are made 
at or near room temperature, it will be sufficient to maintain 
the water at the desired point, as the liquid in passing through 
the submerged part. of the tube to the capillary tip will come to 
the temperature of the water. If the beaker is always filled to 
the same height and the instrument rests on the bottom the de- 
gree of immersion will, of course, be the same. While the re- 
sults thus obtained are only relative, the values for different 
liquids of the same class vary greatly and the differences are 
such as might be expected from their properties. 

In Table XXX a difference in drying oils and thinning liquids 
not shown by the usual surface tension methods is indicated. 
For instance, perilla and chia oils are seen to have a much higher 
interfacial tension against water than has linseed oil. If the 
same relation holds at solid-liquid surfaces (which exists in 
applying the oil to a solid surface) it appears that this higher 
interfacial tension would account for the “crawling” of these 
oils. The low value found for extracted linseed indicates that 
the interfacial tension was reduced by the large percentage of 
free acid. Accordingly it was found that when different per- 
nentages of linseed oil acids were added to a linseed oil of low 
acid value, the interfacial tension was greatly decreased. 

The addition of linseed oil to perilla oil lowers the interfacial 
tension of the latter against water. In the mixture of oils given 
the crawling effect was found to be entirely overcome. While 


* The writers have turned their design over to the A. H. Thomas Com- 
pany, of Philadelphia. This firm has satisfactorily produced the apparatus 
in accordance with the design for $6.89. 


160 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


heating for a few minutes at a high temperature appears to 
lower the interfacial tension, if the heat is continued longer the 
tension again increases. The increase in viscosity, due to pro- 
longed heating, apparently overcomes the surface tension effects 
in the case of perilla oil. 


TABLE XXX—Measurement of the Tension at the Liquid-Liquid Surface . 
Against Water 


All measurments made at 20° C. 


Number 
Liquids of drops 
Bear w Lit See aasecccsccstecnase cnc hes daccyecvucseevessnSbveceneschenntecGlndebdeylsee sce age aaa 55 
Linseed extracted (acid valve 22) oe. ceensceceeeeeseeessssseessemmmnntenceeeesmnmnsseeseeenenaaaunestes 82 
95% Linseed U 70 
5% Linseed acids § webedaceuccecccencccdccwewwnbevecvoaseesusens: acuntoscvetsrs=ssseecedsene= Sees ebeNesSs0necE Bn hones Sse lela Sanaa 
90% Linseed U 90 
10% Linseed acids § chacevenecevececconavnesaaqeccns##®@seunesudecnscuedssugmcontes ou asemereasesnr~nuaeets = —aUnen sae sme. Ges aes eame cme 
80% Linseed l 295 
20% Linseed acids (oe 
Pevil le coecccceccccsscsecececcccesveoncnstcbenusibincntessodteseeceessttetenteceestacendneet hen tncher Set ahenet ete eta oF 
CYL, cecceescssescsascossneeveceeseesvntcsetsteneegnesensnasgnterstesuneinnshnnteanertantaconeroetncr=ot sae eee oF 
Perilla (heated at 230° C. for 10 minutes ) ccc ee 42 
Perilla heated 20 mins. at 2EO0° Coc ccrcccceccceecersssenesesnnneceennenecesmereeemnnnranantessaseats 33 
Perilla (heated at 260° for 2 HOULs) .ecccccccccccsecssneretensmeesanssmnnmernmnaatesentie 30 
Alkali refined Linseed Py RM 
AGid refined Limseed Oil ecccescccccccssoccsesssocsssssssmununseesececeesuseeteetsSuesuaneeseesasesunaunnnaneeteaamesatriaataata 44 
Limsced fatty ACids..eacccceccmeesssecseesseesteessnceseemneesnresnttnsetussunttnneranemnnesersntennesessietaatsaeesee 300 
66 2-3% Linseed | 52 
33 1-3% Perilla § veeecenuecercserscccsuapecasacsuesnsccasenseses sucnsdeacceancancesnee#easscaneueussbasnansuce"ene=tavarenssapsasar=ssenns=aNsc===n8rss 
Varnish makers’ Linseed oil heated at 500° for 2 hours... 36 
Perilla heated to 300° C. rerpric) ya. nnan- ana ecteecccceeecstenns ra eaeens aaa ere eee ~ 35 
Cold pressed Liar 09 natn cee enn ets cc erp terrae nen tee 41 
AA oil (causes pitting Of japars) occ ece estes sensceneeneennennencenneesnmmnannunntnaceae 33 
Wray an cececziccscecccscedesececec,chcsseepcsthtesontcts>neasstlsenasasasbhlp eerancestres ted gedaan 40 
PUY POM ta’ oneceecesneseccseeenetnevneeerstennentuenctntnsensennnenetnebaneuneeesnessnaentes eterna 115 
Mimeral Spirits cceccccssssssecseneesesseseteseenseensornneennnsantttetnetteotanetnueateaiesanerunreseenneeneantcaeeaaaea ge 
Against Salt Solution 
Turpentine ci si-chcekiciete ean pear ee sachisceeseentomsesiablusee este ea 135 
Mimerall Spirits ccc sccccccteeeccsncectecteeseetetrt cancer erfeseee nerd te 89 


Turpentine and mineral spirts which show the same surface 
tension exhibit a very different interfacial tension against water. 
This result indicates that the selection of suitable thinners for 
various types of. paint and varnish liquids is a matter of great 
importance. “ 

All solid surfaces are believed to hold an adsorbed film of 
moisture. Although this film may only be of molecular thick- 
ness, it may yet form a continuous layer between the solid sur- 
face and the applied coat. If such is the case it is conceivable 
that the surface is really liquid-liquid instead of liquid-solid, and 
that the conditions obtaining in the measurement of the inter- 


SURFACE TENSION 161 


De ee 


facial tension against water as described herein closely approxi- 
mate actual working conditions. If this tension is in any way 
related or proportional to the tension which actually exists at a 
solid-liquid surface it should hold for all immiscible liquids. If 
a definite relation holds for the liquid to be tested against any 
immiscible liquid it could more justifiably be used as indicating 
solid-liquid tensions. When determinations were made using 
salt solutions the ratio between the number of drops of tur- 
pentine to mineral spirits was approximately the same as when 
pure water was used. | | 
An explanation for the existence of equal surface tensions in 
liquids of the same kind is advanced by I. Langmuir, who refers. 
it to the arrangement of molecules in the surface layer. He 
states that: , 


The group molecules of organic liquids arrange them- 
selves in such a way that their active portions are 
drawn inward, leaving the least active portions to form 
the surface layer, the active portion of the molecule be- 
ing that part of the field characterized by a strong stray 

. field (residual valence). Surface energy is thus a meas- 
: ure of the stray field which extends out from the sur- 
face layer of atoms. The molecules in the surface layer 
arrange themselves so that this stray field is a minimum. 

The surface energy of a liquid is thus nota property 
of the group molecules, but depends only on the least ac- 
tive portions of the molecules and on the manner in 
which they are able to arrange themselves in the sur- 
face layer. In liquid hydrocarbons of the paraffin 
series, the molecules arrange themselves so that the 
methyl groups (CH:) at the ends of the hydrocarbon 
chains form the surface layer. The surface layer is 
thus the same, no matter how long the hydrocarbon 
chain may be. Asa matter of fact all these many 
different substances from hexane to molten paraffin 
have substantially the same surface energy, namely 
A6 to 48 ergs per square centimeter, although the mole- 
cular weights differ greatly. 

If now we consider the alcohols such as CH:OH, 
C.H:OH, etc., we find that their surface energies are 
practically identical with those of the hydrocarbons. 
The reason for this is that the surface layer in both 
cases consists of CH: groups. 


Accepting the above statement as true, the measurement of 
the surface tension of liquids against air would yield important 


162 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


information in regard to substances of different molecular 
groupings. It will not, however, serve to differentiate in any 
way between liquids which have the same atoms or groups in 
the surface layer. While it is possible that the so-called active 
portions of molecules may be drawn inward at any surface, 
whether air-liquid, liquid-liquid, or liquid-solid, it is probable as 
already pointed out, that the tension in the latter cases has a 
very different value from the former. Different vegetable oils 
may therefore show the same tension against air due to the 
fact that they all present the same group or portion of the mole- 
cule at the air surface, but it is conceivable that in contact with 
another liquid or a solid (pigment) different oils may have 
different groups in the surface layers, particularly if the ac- 
tive groups possess an affinity for the surfaces with which they 
are in contact. We have, therefore, different manifestations of 
the same force depending upon whether we are considering the 
tension between the liquid surface and air or the tension be- 
tween the liquid and another liquid or a solid. 


CHAPTER XVII. 
COLOR STANDARDS FOR VARNISHES 


GARDNER-HOLDT APPARATUS 


Some plant managers consider it of importance to gauge the 
color of certain varnishes so that batches made up will closely 
approximate those produced at previous periods. The usual 
means of accomplishing this is to keep samples for comparison. 
It has been found, however, that varnish samples kept in glass 
and exposed to light, may show a substantial change in color. 
Another method that has been used to some extent is to make 
up a solution of 3 grams of potassium bichromate in 100 cc. of 
pure sulfuric acid, limiting the darkness of varnishes to the 
depth of color shown by such a solution. This solution, how- 
ever, has the disadvantage of being quickly reduced, the yellow 
soon being replaced by a green tint. This change is sometimes 
noticeable on a few hours’ standing. The use of such a standard 
would, therefore, require the making up of fresh solutions from 
day to day. A suggestion has been made that a varnish slightly 
lighter in color than the standard solution of bichromate re- 
ferred to above, be prepared and preserved as the standard for 
comparison. This, however, is not always satisfactory, owing 
to the actual color changes which take place even in varnish and 
to the limitation of having only one standard rather than a 
number of graded colors. 

The writer and P. C. Holdt have found a number of other 
substances that fairly match varnishes in color but which unfor- 
tunately are not permanent. For instance, iodine solutions fade 
in the light, metallic salt solutions such as ferric chloride are 
affected by the alkalinity of glass containers, ultimately throw- 
ing down precipitates and becoming lighter in color. Organic 
dyestuffs experimented with have proved either deficient in red 
or yellow, or subject to rather rapid loss of color upon standing 
in the light. 

In the experimental work that has been conducted an attempt 
was made to use a set of cube rosin standards ranging from 
G. to WW. These were first melted and poured into perfectly 
dry, clear glass tubes such as are used for making the bubble 
viscosity test on varnishes. It was found, however, that upon 

163 


164 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


cooling the rosin would crystallize in the tubes, sometimes de- 
posting long crystalline needles against the glass, causing an 
opacity which would obscure the color. Moreover the grada- 
tions of color shown by the rosin standards were entirely un- 
satisfactory. 

As a result of a series of extended experiments, it was found 
that the substance known as caramel (burnt sugar), when 
diluted with water, produced clear solutions which exactly match 
the yellow amber and red ruby colors produced by various types 
of varnishes. In fact, the color effects produced by different 
strengths of aqueous solutions of caramel more closely approxi- 
mate the colors of varnishes than any other substance experi- 
mented with. After considerable preliminary work, a series of 


TABLE XXXI 


ce. of caramel 


Solution No. | ce. of water. ney FE FS 


Te) 
bo 
ron 
TOR NORM NWN HO On 
obo ROOM HRA io i bo 


= 

° 

on 

ot 

for) 
APN HH 


12 caramel solutions varying in color from almost water white 
to that of the darkish varnish, was prepared from a strong 
solution made by dissolving 15 grams of liquid caramel syrup 
in 450 cc. of water.* This concentrated solution was diluted 
with various proportions of water to secure the desired range 
of colors met with, and ranging from standard turpentine 
to the darkest grades of oleo-resinous varnish. The concentra- 
tion of each solution is given in Table XX XI. In making the dilu- 
tions, both water and caramel solutions were accurately meas- 
ured from a burette. 


* Commercial caramel varies greatly in concentration. Several sam- 
ples were purchased by the writer from various drug stores. The strength, 
however, may easily be adjusted, using as a standard for one sample, 3 
grams of potassium bichromate dissolved in 100 cc. pure sulfuric acid (spec. 
grav. 1.84). 


COLOR STANDARDS FOR VARNISHES 165 


The solutions prepared as above were sterilizezd to prevent 
fermentation and consequent change in color. In determzning 
the best method of sterilization, one set of samples was sterilized 
by heating a weighed amount of solution to boiling for a few 
minutes in an Erlenmeyer flask fitted with an air condenser. 
After boiling, the flask was again weighed and a small amount 
of sterile water added to replace that driven off by the heat. 
In making up another set of samples, one-half of one per cent 
of sodium benzoate was added to each solution. This sample 
was not boiled. A. third set of solutions was made up but was 
not sterilized. These three sets of samples were examined at 
the end of three months. In the set that had not been sterilized, 
there were large masses of fuzzy agglomerates, indicating that 
considerable fermentation had taken place. In the set sterilized 
by heat, there were small amounts of fuzzy masses (possibly 
caused by some contamination in transferring the solutions to 
the sterilizezd tubes). The set of samples which had been ster- 
ilized with sodium benzoate showed absolutely no evidence of 
fermentation. It was decided, therefore, that this method of 
sterilization is the best. Later it was found advisable to use 
25 per cent of alcohol in the solutions. 

To test the permanency of the suggested color standards, the 
color strength of each solution was determined by means of the 
Lovibond tintometer in terms of both red and yellow. These 
readings were then repeated at intervals of from two to three 
weeks to determine whether any change was taking place. The 
same set of tubes was used throughout, being tightly corked 
after each reading. They were kept in the laboratory upon a 
table in the light so as to afford every opportunity for color 
changes. The results on a series of four readings are given in 
Table XXXII. It will be noted that there was practically no 
change in the color of these standards between the first and the 
final readings. Any minor changes indicated were so slight as to 
be attributable to experimental error in observation rather than 
to change in the color of the solution. As a check on the results, 
there was made up on Oct. 12th another set of the standard 
solutions, by using the same lot of caramel diluted to the same 
concentration and sterilized by the same process. When these 
solutions were compared with those made up three months be- 
fore, upon which the readings had been made, no change was 
shown. 


166 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


From a strictly scientific point of view, it would be more 
accurate to measure color strength of varnishes in terms of 
wave length and to look for color changes with the aid of a 
colorimeter. However, a variation in color that cannot be de- 
termined by the unaided eye is of no importance in the pres- 
ent connection, as approximations only are desired. Moreover, 
because of the high cost of accurately standardized colori- 
meters, such apparatus would not be available in most varnish 
factories. It is the writer’s belief however, that a simple form 
of apparatus such as is suggested in this paper, might be pro- 
duced by anyone interested and quite satisfactorily serve the 
purpose for commercial work. 


TABLE XX XII—Color Strength of Caramel Solutions (Lovibond Tintometer) 


Ist Reading 2nd Reading 3rd Reading 4th Reading 


Sam- | Size July 7th. July 15th. July 28th. Aug. 22nd. 
ple Cell. | eee 
No. 
Yellow. | Red. | Yellow. | Red. | Yellow. | Red. | Yellow. Red. 
Ostet os yy" 2.0 0 2.0 0 230) OT 2a .0 
eee yy" 5c ae a.0 > 3.0 ue 3.0 he 
Yat gee ly" boo) “2 5.0 2 5.0 Lg 5.0. se 
ete, yy” 8.5 2 8.5 3 8.5 3 8.5 72 
a ee 1" 16.0 eT 16.0 oni 16.0 he 16.0 8 
Y peer Meng Ss 26.0 9 26.0 Pot 26.0 1.35) 26.0 1.35 
Pe ae yy” 36.0 2 36.0 26 36.0 3:0 36.0 3.0 
DO eae 30.0 1:75) 30.0 1 7514308 7a Oe ees 0) 1475 
HG eres yr 42.0 4.0 42.0 4.5 42.0 4.7 42.0 4.5 
Liccie yy" 51.0 ica HzO 8.0 51.0 8.0 51.0 ee 
Lee yy" 61.0 12-5 61.0 5 ra 61.0 1256 61.0 12.5 


Nore: Because of the very light color (match for turpentine) of Sample No. 1 
this was not included in the readings. . 
In order to test the permanency of the color of varnishes, 
samples of exterior varnish, floor varnish, and rubbing varnish 
of well known commercial brands were selected. These were 
placed in tubes in the original undiluted condition, and also 
diluted with 25 per cent and with 50 per cent of pure spirits of 
turpentine. Five sets of tubes thus prepared were sealed air- 
tight in viscosity bubble varnish tubes. Two sets of these sealed 
samples were wrapped separately in heavy paper, placed in a 
box so as to completely exclude all light, and so prutected until 
the time of making a reading for color value. Two other sets 
were exposed to ordinary daylight in the laboratory but not to 
the direct rays of the sun. Readings were taken on one set of 


—R—— ie ee 


COLOR STANDARDS FOR VARNISHES 167 


the sealed tubes kept in the dark and one set kept in the light, at 
the end of periods of one month. On the sets kept in the dark, 
no appreciable change was observed at the second reading. The 
sets kept in the light, however, showed considerable change. 
Readings on the latter are given in Table XX XIII. The change in 
some of these was sufficiently great to be easily detected by 
the eye without the use of an instrument. It is very interesting, 
however, to note that the change is not always a lightening of 
color. For instance, some samples had become very much darker 
in color. 


TABLE XXXIII—Readings on Varnishes Exposed to Light, Showing Changes 
in Color Values 


; 1st Reading 2nd Reading 3rd Reading 
Aug. 22, 1921.| Sept. 13, 1921.] Oct. 11, 1921. 
Sample. (2) be PRS Tel ree pty Bae Se Seis a OC & 

Yellow. | Red. | Yellow. | Red. | Yellow. | Red. 

Exterior Varnish....... yy" 42 1.1 36 123 ‘33 Vege: 
Ext. Varnish 25% Turp..| 1” 32 0.8 30 0.5 28 OSD 
Ext. Varnish 50% Turp..| 1%” 28 0.5 23 OS ve 0.4 
Floor Varnish.......... yy” 65 320 62 305 61 3.0 
Floor Varn. +25% Turp.| 4%” 52 11 50 i loge) 45 1.1 
Floor Varn.+50% Turp.| %” 36 0.1 34 0.1 ee 0.1 
Rubbing Varnish....... yr 42 5.6 43 6.2 46 6.2 
Rubbing Varn. 25%Turp| 14” ol 4.3 36 4.2 38 4.0 
Rubbing Varn. 50%Turp| 14” 42 5.0 48 6.0 50 6.0 


The same combination of glasses was used in successive readings to deter- 
mine whether there had been any change in color. This vrocedure is nec- 
essary because the combined thickness of the glasses affects the reading. 
For instance, a sample may match glasses 16 + 14 +8 but be lighter than 
than a combination of glasses 16+ 14+672. In the second and third 
readings, the same combinations of glasses as were found to match the 
sample in the first readings were tried. Changes were then made until 
the glasses matched the samples. In Tables XXXII and XXXIII only total 


readings are given. 


In considering the set of 12 solutions reported on in Table 
XXXI, it was found possible to omit samples 3 and 5. This lefta 
series of 10 standards. Standard No. 1 is the equivalent to 
“Standard” for turpentine, in accordance with the Interdepart- 
mental specifications of the U. 8. Government for this material. 
Standard No. 9 in this new set is the equivalent of the bichomate 
solution used as a standard for gauging varnishes in accordance 
with the Interdepartmental specifications for spar varnish. 

These 10 new standards, made up as outlined above and now 


168 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


containing 25 per cent alcohol to further guard against fermen- 
tation are sealed in glass tubes with corks and viscose tops. 
These are placed in a special carrying case similar to that used 
for the bubble viscosity test standards. The upper part of the 
case bears a label giving the color strength in red and yellow of 
each sample in accordance with Table XXXIV _ shown below. 
These tubes as made and standardized at the writer’s laboratory 
are widely used throughout the industry. 


TABLE XXXIV 
Stats Ce. of Ce. of Size Combination of Glasses in 
ON, <— W : i Caramel of ; Lovibond Tintometer to 
on ater | Solution! | Cell match sample 
1 99.8 0.2 VY" Yellow Red 
2 99.6 0.4 VAG 2.0 0.0 
5 97.6 2.4 1" 5.0 0.2 
4 92.6 7.4 4" | 16.0 0.8 
5 88.9 1h 4" -* 16+10=26 Pele sh 
6 81.5 18.5 1" 16-+-14:-6 = bee Wiese 
se. Sees te 
7 72.2 27.8 1" 16-+14—30 S78, 
8 55.6 44.4 yr 164+14412=42 | 4.5 
9 40.8 59.2 yr 164+14412+49=51 7.5 
10 22.2 | 77.8 yw" | 164144124104+9=61 [°12.5 | 


ee ren) 


1 Solution made of 15 grams commercial caramel syrup in 450 ce. water. 


No. 1 equivalent to limit of color for turpentine, U. S. interdepartmental 


Comm. on Paint Specifications, Recommended Standards for Turpentine. — 


No. 9 equivalent to limit of color for Spar Varnish, U. S. Interdepart- 


mental Comm. on Paint Specifications, Recommended Standards for Spar 


ae 3 grams potassium bichromate to 100 cc. Sulphuric Acid (Sp. 
108 x e 2 tt ; : . } 


CHAPTER XVIII. 


TESTING THE SPEED OF EVAPORATION OF THINNERS 
FROM PAINT AND VARNISH FILMS 
WITH A DISCUSSION OF THE VISCOSITY EFFECTS INDUCED 
BY VARIOUS HYDROCARBONS 

Oleo-resinous varnishes usually contain from 40 to 60% of 
“thinners” such as turpentine, mineral spirits or similar organic 
volatile liquids having quite wide variations in boiling points. 
The rate of drying of such varnishes has been considered as de- 
pendent to some extent upon the character and amount of thin- 
ners present. 

That mineral spirits will evaporate more slowly than turpen- 
tine from a varnish film is well known. The effect of the type 
of hydrocarbon upon the rate of evaporation has heretofore ap- 
parently lacked investigation. The proportion of the various 
fractions of widely different boiling points which make up the 
hydrocarbon thinning liquids is also a matter of considerable 
importance. In addition to the influence of the above factors 
upon the drying of a varnish may be mentioned the effect of 
the thinner upon the viscosity of the thinned varnish. The ex- 
periments described herein were conducted for the purpose of 
securing information along the above lines. 

In order to secure exact data on the subject a series of 
thinners of widely varying boiling points—namely, turpentine, 
mineral spirits, solvent naphtha, benzine and benzol—were ex- 
perimented with. The varnish bases were prepared in a varnish 
plant in 100-gallon kettles. One was a short oil interior 
rubbing varnish containing about 7 gallons of varnish makers’ 
linseed oil to 100 pounds Kauri gum; the other a long 
oil spar varnish containing about 24 gallons of Tung oil and 12 
gallons of alkali-refined linseed oil to 100 pounds of combined 
varnish resins. These varnish bases were sent to the laboratory 
without added thinner. 

The varnish solutions were prepared by warming the base 
until it became liquid enough to incorporate the thinner, care 
being taken to avoid excessive heating. Both base and thinner 
were very carefully weighed* before mixing. All samples were 


* Results throughout are based on percentage of volatile by weight. 
169 


170 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


rewelghed after mixing to insure that there had been no appre- 
ciable loss of volatile during the mixing. In no case, except 
with certain of the lower individual fractions, was the loss suf- 
ficient to require further addition of thinner to secure the de- 
sired percentage of ingredients. The amount of thinner did not 
vary in any case by more than a fraction of 1% from that shown 
in the tables. 

In Table XX XV is presented a distillation chart of the various 
thinners used. The mineral spirits were of a high grade com- 
mercial type meeting the specifications of the U. S. Interdepart- 


FIGURE 79 


Weighing Bottle Used in 
Tests 


mental Committee on Paint Specifications. Benzine, benzol, and 
solvent naphtha were average commercial samples of good qual- 
ity. The turpentine was a few months old and left a rather high 
viscous residue, but was satisfactory otherwise. 

Small bottles were tightly fitted with corks into which were 
fastened small brushes. (See Fig. 79.) A few grams of varnish 
were poured into one of the bottles, and the cork set tightly in 
place so as to prevent evaporation. The bottle, with its brush 


tal 


SPEED OF EVAPORATION 


*pIostA puv 
uMOIQ YIep oNnpIsey 
% OOT % OOT % OOT % OOT % OOT % 0° OOT 
G ol 61 3V G ol 61 FV tS oL0G 3V G ol GI FV g 0006 3V GaG o9 LG FV 
86 ol 6L 4V 86 ol 61 IV 26 oL0G 3V 86 olGI 4V $6 0006 IV ¢° 16 o9 1G IV 
8 T6I-921 8 L6T-921 L LOG—06T 8 TGI-1Ol g 00c-9LT Gee 9TS—GOG 
OL 9LI—-69T Ol 9LT—-OLT Ol 061-691 Ol TOT—-¥6 OL 9Z1-F9T Ol 60G-F61 
Or 69I-S9T Or OLT-L9T Or 691-9ST OL ¥6 —06 Ol VOI-1L9T Or F6I-L81 
OL S9OT—-E9T OL ZOT-S9T Ol 9SI—-FPFI OL 06 —88 Or T9I—O9T Or L81-Z81 
Or €9T-e91 Or COlseoT OT PVI-VEL OL 88 —L8 OL O9T—O9T OL o8I-6LT 
OL c9I-19T OL S9I-—c9l OL FET-ZET Or 28 —98 OL O9T—6ST OL 6Z1-GLT 
OL T9T—691 Or c9T—O9T OL 6GI-6IT OT 98 —S8 Or 6ST-8ST Or GLI-TZT 
OL 6S1—-6ST OL O9T—-6¢1 Or cII-ZOl OL G8 —G8 OL 8SI-LST Or TZT-891 
OL 6ST-9ST Or 6ST-8ST Or GOI—06 Or c8 -¥8 OL LST—9ST Or 89I—-S9T 
Or 9ST—-FST OL SSI-GGI OL 06 —-T9 OT ¥8 —08 OL OSi=cuT Or SOlL-EST 
P29 stp Oo PeTTHstp ‘Do PeTsip ‘Oo PeTssitp ‘Do P2Tstp ‘Oo Pon PIP Hai 
938 jUI0IOg ‘duiay, || osezuI010g ‘duraj, || osequo010g ‘duiay, || esvquoo10g duiaj, || odeque010g ‘duleay, || ssejuoo1eg ‘dwio J, 
}! 
«Wy, Spads 
[BIBUIUL payeVUOlPRIT eyydeu-JuaA[og eulzueg (06) 1OzGeq oulyuedin J, Syd [BIOUTT\L 


YlOM 24) UL pas suauumy yz fo uoynusiq of abungy ainzosadwayz HbumoyS—AXXX ATAVL 


"* -onpiseyy 
ese 1890, 


UOTPOBAT 


sy[nsey jo ydeay 
SALNNIW NI SWIL 
Sol sl Sc! 4 a Ol 06 GZ 09 14 


HSINUVA Yds 


SLIUIdS WWYSNIW « 
10ZN3qg > 
INIZN3Q + 

INILN3dYNY © 


FIGURE 80 


EXAMINATION OF PAINTS, VARNISHES AND COLORS 


172 


NOILVYOdVAQ SOVLNS0Y43d 


173 


SPEED OF EVAPORATION 


s}nsey jo ydeary 


SILANIW NI SWI 
sol OSI Gs 021 Coles ees $2 09 cy o¢ SI 


- Ol 


HSINYVA YOIMSLNI 


SLIUIGS TVYSNIN 2 
10ZN3g > 
SNIZN3Q + 

JNILNadYNL® 


NOLLVYOd YAW AVLNAD Yad 


FIGURE 81 


174 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


and contents, was then weighed. The cork was then removed 
with its contained brush and the varnish thereon quickly applied 
to a weighed glass plate. The bottle was immediately corked 
and reweighed. The difference in the weight of bottle and con- 


tents before and after applying the film gave the weight of the 
film. 


Approximate Viscosity of Spar Varnish Thinned with Various Thinners in 
the Proportion of 50 Parts of Varnish Base to 50 Parts of Thinner 


Paraffin Petroleum Thinners 


Poises 
| >1-5 (V4 (ene CS 1.65 
150-160° C. Fraction... 2.00 
Fractionated Mineral Spirits “A”..02 3 2.35 
Mineral Spirits cccccsccospc a kscectatncstcetsleunpeekele sae 8.20 
175-181° C. Fyre cti orn icc cecil 3.20 
200-215° Co. Fraction cio tees os 4.00 
Equal Mixture of Fractions (175-181° C. and 225-235° C.)...... 6.00 
225-235° Cx react miosis scescnsssaictove-oseetsseesonens enna eee 7.00 
ZBOO-265° CC. Bret race ecc ss cdsssnossosonsonsgecoope cadezads cokes cepa 9.00 

Cyclic Hydrocarbons 

Benzol 90°" 2 ee ee ee seoensposnseisthisisste pee ee 4.00 
Solvent Naphthea. cosscicoccic3-teccccsc susie enced en 2) 800 
TVAYPemtae on sacesseectcpctentaretbbvanitlsneeryseinestsnteaes oc 10.00 


Similar work has just been conducted by the writer on volatile 


solvents used in making Pyroxylin Lacquer Coatings (see Fig. 
102, page 290). 


CHAPTER XIX. 


EXAMINATION OF TURPENTINE AND MINERAL SPIRITS 


Methods for distillation range, polymerization values and simi- 
lar requirements for thinners are given in the specifications for 
turpentine and mineral spirits in the back of this volume. 
Further methods of examination are given in this chapter. 

Evaporative Value.—Physical and chemical methods for the 
examination of turpentine and mineral spirits are given in the 
specifications of the Interdepartmental Committee that are 
bound in the back of this volume. With mineral spirits, less 
uniform grading is found in commercial practice than with tur- 
pentine. For this reason manufacturers of paint and varnish 
often experience considerable difficulty in securing uniform and 
standard types of mineral spirits for their work. Therefore, in 
addition to the tests prescribed in the specifications referred to, 
it is well for the chemist to make a study of the evaporative 
value of various grades of mineral spirits submitted. For this 
purpose a good exterior and a good interior varnish base may 
be selected, heated, and thinned with about an equal quantity 
by weight of mineral spirits of the grades being tested. The 
varnishes may then be applied to weighed glass plates which 
should be re-weighed every fifteen minutes for a period of two 
hours. The loss in volatile is then reported. (See Circular 
No. 141 of the Scientific Section.) Mineral spirits having large 
quantities of heavy, non-volatile ends will readily be noticed. 
The body of the varnishes and the brushing, flowing and level- 
ing properties should also be ascertained by further tests. 

Solvent Properties.—It is also advisable to make a test to de- 
termine the solvent properties of the mineral spirits, and for 
this purpose it is customary to use varnish bases as referred to 
above, thinning down with equal parts by weight of the mineral 
spirits being tested. The reduced samples are generally placed 
in 4 oz. oil bottles and inspected for a period of 10 to 12 days 
to watch for the development of suspended matter, turbidity or 
other precipitated products due to lack of solvent properties of 
the thinner. Distillation of a sample of the mineral spirits and 
examination of the various fractions for solvent properties often 
gives much information of value. 

One of the most useful materials to include in a test for the 


175 


176 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


solvent character of mineral spirits is extremely heavy-bodied 
linseed oil. Apparent solution takes place when such an oil is 
thinned with mineral spirits, but after standing, the oil is often 
thrown out, showing that the preliminary solution was only of 
a suspension colloid type. The continued addition of increments 
of mineral spirits to a volume of heavy-bodied oil, until the 
precipitation point is reached, will give relative data of almost 
quantitative character. Since such oils are often used in flat fin- 
ishes which sometimes contain in the liquid portion as high as 75 


Begins to cloud Separation occurs | 
Thinner TT 
Oil Thinner Oil Thinner 
DS a a a 1 2 1 3 
Oe oka oe eee 1 8 1 8 
Boh CaP ee ae No cloudiness or separation at any dilution. 
reer eS eae 10, |e rm 
| OND a tee ee Mp manee Py essen A te, 7: No cloudiness or separation at any dilution. 
J 5 peeled (ha co wey Riccar 1 ck aa eae 1 3 | 1 4 
Ke oth as ee ae 1 3 1 4 
Vos ws 6G aie ak ee ee 1 8 1 10 


per cent of mineral spirits, the throwing out of the oil would be 
a very objectionable feature. 


There appears to be a great difference in the action of the 
various brands of mineral spirits with bodied oils, especially 
blown oils. Turpentine usually mixes well in all proportions 
with such oils. When equal portions of the same oil and min- 
eral spirits are mixed, some samples show a turbid and milky 
appearance. As the quantity of thinner is increased the tur- 
bidity increases until separation occurs. While in some grades 
cloudiness occurs even at low dilution, other samples may not 
become turbid until much greater dilutions have been reached. — 
Some may remain clear when mixed in practically any propor- 
tion. Where there is only a slight turbidity at first, complete 
separation may occur on standing. The accompanying chart 
shows the dilutions at which cloudiness and oil separation first 


TURPENTINE AND MINERAL SPIRITS 177 


occurred when thinning a very heavy grade of blown and heat- 
treated linseed oil with several commercial grades of mineral 
spirits. Figures indicate parts by weight. 

In making these dilution tests a tall narrow beaker may be 
conveniently used. A fair idea of the miscibility of the thinner 
may be obtained in the following manner: Weigh out a small 
quantity of bodied oil, say 5 or 10 grams, in the beaker. Then 
add an equal quantity of the mineral spirits to be tested. Stir 
with a glass rod, noting the readiness with which the two layers 
mix. Some samples will show a cloudiness at once, which may, 
however, disappear as the two mix. Others may mix per- 
fectly clear. Add successive portions of the thinner, stirring 
after each addition and noting carefully the appearance, readi- 
ness of mixing, etc. Determine the point at which a permanent 
milkiness results. After the addition of one or two more por- 
tions, part or all of the oil will usually separate on standing a 
short time. | 

While the quantity of thinner required to throw out the oil 
may in many cases be far in excess of the proportion ordinarily 
used, yet in consideration of the fact that the products which 
exhibit the greatest tendency to become turbid are most likely 
to separate on standing, it seems advisable to employ only those 
which stand up best under the dilution test. 

Run Kauri Test.—Another test of importance can be made 
with standardized run Kauri gum such as is used for testing the 
elasticity of varnish. The preparation of this is outlined in the 
specifications for spar varnish in the back of this book. The 
Run Kauri is dissolved in an equal quantity by weight of re- 
distilled turpentine. To 50 cc. of the mixture, mineral spirits 
is gradually added with occasional shaking until a cloud forms. 
An improvement in the test is to use a mixture of 100 cc. of the 
Run Kauri solution and 100 cc. of heavy bodied oil, subsequently 
thinning down a determined volume of this mixture with the 
mineral spirits under examination. For this purpose however a 
standard grade of heavy bodied oil should be used in every lab- 
oratory, otherwise different results would be obtained. 

Whether the thinner is derived from an asphaltum base or 
paraffin base petroleum is of little importance so long as it con- 
forms to other requirements. The asphaltum base petroleums 
are said to possess, in general, greater solvent power due to the 
presence of a larger proportion of cyclic hydrocarbons. If de- 


1) J D 


Ten gram samples of heavy bodied linseed oil placed in each 
bottle. A different grade of mineral spirits added to each. When 
cloudiness was shown, addition of mineral spirits discontinued. 
Only small quantity required to cloud and throw out oil in test D. 
Considerable required to cloud test J. Test F shows no cloudiness 
and is miscible with oil at all dilutions. 


Flat paint liquid 
thinned _ with 
grade of thin- 
ner that has 
caused separa- 
tion of the bodied 
oil. 


FIGURE 82 


Two samples of the same varnish thinned with 
different grades of mineral spirits. Note dark 
color of one caused by reaction between the sul- 
phur content of the mineral spirits and the dis- 
solved lead drier in the varnish. 


TURPENTINE AND MINERAL SPIRITS E79 


sired, the proportion of the latter may be estimated compara- 
tively by the Formolit Reaction (Nastjukoff Test).* But prac- 
tical tests, such as those described herein must remain the de- 
ciding ones in determining the value of a given thinner. 


Sulphur Content.—Another very important observation to be 
made on mineral spirits is the effect of the sulphur content upon 
the color of paints or varnishes in which they are used. The 
white lead test that has in the past been used for this purpose 
will not very often disclose the presence of objectionable sulphur 
compounds. The Doctor test is not sensitive and is rather dif- 
ficult to perform. Varnishes, however, which contain metallic 
driers, such as lead, in organic solution, will rapidly become 
darkened when thinned with mineral spirits containing certain 
objectionable sulphur compounds. Some grades of mineral 
spirits, for instance, may contain as high as 114 per cent of 
sulphur. If this sulphur is in a certain fixed form, it may not 
darken with lead compounds in solution. Other grades of 
mineral spirits, which contain even very small traces of sulphur 
in readily available form, will quickly darken organic lead solu- 
tions. One test which the writer has used is as follows: 


Make up a varnish base by fusing 100 grams of rosin 
with five-tenths of a gram of lead oxide. If desired, co- 
balt, manganese, copper and other oxides that are liable 
to be present in a cooked varnish, may also be included 
in small amounts. This is then used as the base for 
test. 100 grams of the product is heated and thinned 
down with 100 grams of the mineral spirits to be tested, 
and held at a temperature of about 350° F. for 30 
minutes, preferably in a reflux condenser. Darkening 
will occur with those grades of mineral spirits having 
reactionable sulphur content. 


Probably the most graphic test for sulphur in mineral spirits 
is the copper strip test. This is made by placing in a carbon 
tube about 15” long and 14” in width, a strip of copper 14” wide 
and 2” long. Sufficient mineral spirits is added to completely 
cover the copper. The tube is then immersed in an oil bath 
which is run up to 350° F. or to such temperature as will cause 
the mineral spirits to boil. The test should be run for a period 


* See Holde-Mueller, Examination of Hydrocarbon Oils and Saponifiable 
Fats, John Wiley & Sons, p. 38. 


180 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


of 30 minutes, and the effect on the copper strip observed. If 
only a slight bloom or fluorescence is shown, the mineral spirits 
should be acceptable. If blackening of the strip is shown, the 
mineral spirits should be looked upon as unsatisfactory for 
certain varnishes. This test will show a blackened condition of 
copper if the mineral spirits contains even .04 per cent of re- 
active sulphur. 

It has been proposed to run the copper strip test at a higher 
temperature, keeping the strip in a flask of boiling mineral 
spirits, connected with a reflux for ten minutes and then dis- 
tilling off about 96% of the mineral spirits. Such a test would 
appear rather severe. 

Distillation Range.—Better control of boiling range by the re- 
finer will enable him to deliver a more satisfactory product to the 
consumer. Mineral spirits conforming to Federal Specifications 
(see back part of this volume) while generally satisfactory for 
thinning paste paints, would be of much greater value for thin- 
ning varnishes if of a narrower range in distillation. The 
Philadelphia Paint Production Men’s Club suggest the following 
range: : 

Distillate below 150° C. not over 5%. 


. Distillate below 180° C. not less than 50%. 
Distillate below 220° C. not less than 97%. 


CHAPTER XX. 


TESTING ALUMINUM STEARATE 


ITS CHEMICAL AND PHYSICAL PROPERTIES AND USE IN 
THE PAINT AND VARNISH INDUSTRIES 


Aluminum stearate has been used in considerable quantities 
during recent years, in, the paint and varnish industries. It is 
used for producing certain physical conditions, such as body and 
non-settling in prepared paints; waterproofing and flatting prop- 
erties in interior wall paints, and to induce a rubbed-finish ap- 
pearance in some furniture varnishes. The extent to which these 
conditions are obtained in a product appear to depend upon or 
be related to the degree of viscosity which the stearate will im- 
part to the liquid, which, in turn, is influenced by the purity, 
texture, etc., of the stearate. 

Several manufacturers using aluminum stearate have experl- 
enced difficulties due to non-uniformity of different lots re- 
ceived.* In the present investigation it has been found that 
different brands vary greatly in both chemical composition and 
physical properties. In view of the variation of the different 
brands, it would seem desirable to have specifications, com- 
pliance with which would insure the suitability of the material. 

Visual Examination.—For the present investigation, a num- 
ber of samples were obtained from producers and users of 
aluminum stearate. It was found that much could be learned 
concerning their suitability by visual examination. For in- 
stance, those samples which are readily soluble and which 1m- 
part the higher viscosities to solutions are almost invariably the 
ones that are finely divided. When stirred up in a liquid, color- 
less paraffin oil, for instance, the more finely divided stearates 
yield milky liquids in which no coarse particles are visible. Other 
samples (coarse) contain lumps or agglomerates which do not 
break up on stirring and settle very quickly. When examined 
under the microscope some samples are seen to be of fine texture, 
and the particles, although apparently not crystalline, are 
clearly defined and fairly uniform in size. In other samples the 
material is seen to be more or less agglomerated and presents a 


*The investigation to date has been facilitated by the suggestions of 
Dr. P. S. Kennedy and Mr. H. M. Johnson, of the Murphy Varnish Co. 


181 


i 
ph 


182 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


very non-uniform appearance. In those samples examined, 
which were found to contain free stearic acid, the particles of 
the acid could readily be detected under the microscope by their 
semi-transparent appearance. 

Solubility—Aluminum stearate does not appear to dissolve 
appreciably in any solvent in the cold. It goes into solution in a 
number of solvents quite readily, however, when heated. When 
a mixture is heated, the stearate apparently softens and then 
melts as the temperature is raised, subsequently being dispersed 
through the liquid.. The character of the solution formed by 
the various stearates differs greatly. For instance, in certain 
concentrations in a given solvent, one stearate will yield only a 
thin liquid while another will yield a solid gel. With certain 
samples precipitation occurs upon standing, and the appear- 
ance of the solution changes, while in other cases no change is 
observable. 

Solutions of samples Nos. 1 to 7 in turpentine, mineral spirits, 
and benzol were made. In each case 10 grams of dry stearate 
and 200 c. c. of solvent were used. The stearate was dissolved 
by heating the mixture under a reflux condenser. In Table 
XXXVI observations made during the test are tabulated. It is 
realized that, in actual practice, stearates would probably not be 
used in this manner, but the test, nevertheless, throws some light 
on the possible behavior of different samples when used in the 
ordinary way. 

Remarks.—As stated above, a definite temperature is neces- 
sary for bringing a given sample of stearate into solution in any 
solvent. The boiling points of both turpentine and mineral 
spirits are considerably above the melting point of any sample 
of stearate. As a result the stearate melts and is dispersed 
through the liquid, forming a colloidal solution or gel. It is be- 
lieved that the nature of the colloidal body formed determines to 
a large extent the value of a given sample as an ingredient of 
paint and enamel. It should be noted, however, that the turpen- 
tine solution of some samples differs markedly from the mineral 
spirits solution of the samples. | 

Benzol, on the other hand, boils at a temperature considerably 
below the melting point of aluminum stearate. Since dispersion 
of the stearate does not occur to any considerable extent much 
below its melting point, only a small quantity of it is taken up 


183 


ALUMINUM STEARATE 


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‘<pnop JeyMowios ‘snoosta AIBA ‘AoUOASTSUOD WOFIUN ‘peT[es ‘T ‘ON : : 


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SUOI}NIOS SuUIyVUl 


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ES 


jozuag pun spudg jovaurpy ‘auyuaduny, us sazv.1n07G fo wo17zNjoS—TAXXX ATaVL 


184 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


by this liquid even after prolonged heating. In the solution 
made as indicated above, the liquid, when poured from the un- 
dissolved portion, was more nearly a true solution than is pos- 
sible to make in even dilute solutions in turpentine and mineral 
spirits. By the use of the higher homologues of benzol, how- 
ever, it is possible to make much more concentrated and more 
viscous solutions. 


VISCOSITY AND CONSISTENCY TESTS 


Jelly Test.—One manufacturer* of sterates uses as a control 
test a so-called jelly test. This test presumably indicates rela- 
tively the degree of viscosity that different samples will impart 
to a liquid. It is carried out as described below using the ap- 
paratus shown in Fig. 83: 


Heat 10 grams of aluminum stearate with 90 c¢. c. 
crude paraffin oil in a beaker of 200 c. c. capacity to a 
temperature of 150° C. Stir the mixture constantly 
while being heated. When solution is complete, cool to 
about 10° C. 

By this treatment a jelly is formed, which varies 
with different samples from a soft, oily mass to a hard, 
solid gel. 

The firmness of the gel thus made is tested by means 
of the apparatus shown in Fig. 88. The beaker con- 
taining the gel is placed under the plunger. On the 
small scale pan on top of the plunger another beaker is 
placed, and into this mercury or shot is poured until the 
gel yields under the pressure. The weight taken is the 
total weight of mercury, beaker, and plunger. 


As stated in a communication from the above concern, this is 
a rather crude test, being intended only for comparisons. It 
should be made on the various products under consideration at 


the same time and under the same conditions. - It is further | 


stated that when carried out as directed above, results will not 
check closer than 15 or 25 grams. 

An apparatus was assembled and this test was applied to the 
samples under investigation. It was carried out as described 
above, the gels being held at 10° C. for two hours to insure a 
uniform temperature. In check determinations the results 
differed considerably, sometimes varying as much as 20 per cent. 
The difference between different samples is so great, however, 


*Mallinckrodt Chemical Works. 


185 


ALUMINUM STEARATE 


oy 
9,8 
( 

es 


aati 


sS 


FIGURE 83 
Apparatus for determining strength of gel made of Aluminum Stearate. 


186 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


that even with this great variation the test may be of value. In 
making gels of different samples for a comparative test the same 
oil should be used for all samples as the firmness of the gel is 
slightly influenced by the viscosity of the oil. 

Considerable information is obtained by observing the be- 
havior of the material during the process of heating and the ap- 
pearance of the gel after cooling. In the opinion of the writer, 
these observations are more important than the firmness test. 

Solutions of stearates in turpentine and mineral spirits are 


FIGURE 84 
Two Samples of Aluminum Stearate in Mineral Spirits After Standing One Month— 
Sample on right (No. 


Sample on left (No. 1) uniform consistency, mass is a solid gel. 
4), shows a thin liquid phase and a fairly firm gel that has slumped down. 


ALUMINUM STEARATE 187 


not suitable for consistency measurements because of their non- 
homogeneous nature. Solutions in paraffin oil may gel to a 
certain extent,-even at low concentrations. Benzol solutions of 
definite concentration are not readily made, as a portion of the 
sample usually remains undissolved. A further difficulty arises 
from the fact that the consistency of the above solutions may 
change materially with the slightest agitation, due to a breaking 
down of the gel structure. For instance, when attempts were 
made to measure the viscosity of paraffin solutions by the tube 
test, it was found that the inversion of the tube alone was suf- 
ficient to cause a considerable change in consistency. 

The ‘‘viscosity induction” of a given stearate may, however, be 
measured by the tube method, using a xylol solution. Xylol gives 
the same type of solution as benzol, and on account of the high 
boiling point of xylol, the stearate can be heated sufficiently high 
to obtain the desired concentration. This method, while not en- 
tirely satisfactory, yields good results if definite conditions are 
maintained. Below a certain concentration, aluminum stearate 
dissolves on boiling in xylol to a colloidal solution fairly free 
from suspended matter. The consistency does not appear to be 
greatly affected by agitation due to handling the container, and 
remains constant over a short period of time. It changes, how- 
ever, with age, usually becoming thinner. It is, therefore, neces- 
sary to make consistency determinations at a fixed time after 
preparing the solutions in.order to get concordant results. The 
exact procedure was as follows: bas 


. Three and a. half grams of stearate were weighed into — 
a 250 cc. Erlenmeyer flask and 100 cc. xylol added. The 
liquid was boiled for a few moments under a reflux con- 
denser. The solution was allowed to cool under the 
reflux and then removed and stood aside for two hours, 
taking care that none of the solvent was lost through 

- evaporation. The viscosity of this solution was de- 
termined in the usual way by the tube test, making the 
test at about 25° C. 


Johnson uses the following method for measuring the viscosity 
of paraffin oil-stearate solutions : | 


Dissolve 5 grams of stearate in 100 cc. paraffin oil by 
heating to 150° C. - Dip a marked spatula into the solu- 
tion to the mark, and allow to drain until definite drops 
come off. Allow a drop to fall on a glass plate inclined 


188 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


at an angle. The drop will flow down to a greater or 
less distance, depending upon the viscosity of the solu- 
tion. The distance of flow gives a relative measure of 
the viscosity of different solutions. 


CHEMICAL EXAMINATION 


Moisture.—Different lots of stearate vary in the amount of 
moisture which they contain. 

It may be determined in the usual manner—that is, by heat- 
ing about 1 gram of the sample in an oven for 3 hours at about 
105° C. A method used by Johnson gives somewhat more con- 
cordant results, and is probably more accurate in the case of low 
melting point stearates. The latter method is carried out as 
follows: 


Carefully desiccate a quantity of oleic acid by drying 
in a moisture oven for several hours. Weigh into a 
small portion of the desiccated acid about one gram of 
the sample. Heat at 105° C. for 3 hours and determine 
the loss in weight. 


While the percentage of moisture is usually relatively small, 
it appears to influence the gelling properties of the sample, or to 
be related to it in some way. Several users -specify a low 
moisture content stearate, and at least one manufacturer at- 
tempts to keep the percentage in his product at 0.5 per cent or 
less. Upon the suggestion of E. J. Cole, several experiments 
were made to detremine the effect on the gelling property of 
water soluble compounds that may be present.. Small quantities 
of water, sodium sulphate solution, and sodium hydroxide solu- 
tion were added to separate 10 gram portions of No. 1 stearate. 
To each, 90 ¢. c. paraffin oil was added and the mixtures gelled 
as described in the jelly test. The samples to which pure water 
and sodium sulphate solution were added yielded gels apparently 
as firm as when nothing was added. The sample to which 
sodium hydroxide (a fraction of one per cent) was added, re- 
mained very thin throughout the entire heating, and when cold 
was very soft, similar to Nos. 6 and 7. The appearance was that 
of a highly refined Petrolatum Jelly (vaseline), for which it 
might serve in some arts. Apparently caustic alkalies have a 
very marked effect upon the jelling of Aluminum Stearate. 

In Table XX XVII are given the moisture content and water 
soluble in the samples examined. In general the samples of 


ALUMINUM STEARATE 189 


en —————— 


FIGURE 85 

Appearance of Three Gels Made of Alumi- 
num Stearates in Paraffin Oil—Upper sample 
(No. 12) is very white and crumbly. Middle 
sample (No. 1) fairly white and crumbly like 
polymerized Tung Oil. Sample (No. 6) at bot- 
tom is soft and smeary like vasseline. Note 
how it flows. 


190 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


lowest moisture content have the smallest proportion of water 
soluble. Table XX XVII, studied in connection with the experi- 
ments described in the previous paragraph, indicates that while 
the percentage of moisture may not in itself necessarily influence 
the viscosity of stearate solutions, yet it suggests the presence of 
compounds which do have this effect. 

Total Ash, Aluminum Oxide, and Water Soluble.—The de- 
termination of these constituents is an important part of the 
chemical examination. They are easily and quickly determined, 
and are valuable indications of quality. Of the samples under 
investigation, those which have the lowest viscosity induction 
values have a high percentage of water soluble, while in those 
yielding the most viscous solutions, the water soluble content is 
very low. These determinations were carried out as follows: 


About five grams of the sample was weighed into a 
silica crucible and carefully ignited over a Bunsen 
flame. The residue was reported as total ash. The 
crucible was then placed in a 400 ec. c. beaker and 
treated with boiling water to dissolve the water soluble 
portion. The solution was filtered through a quanti- 
tative paper and the paper burned in the same crucible. 
The second ashing represents Al: O: with the traces of 
iron and other impurities that may be present and the 
difference between the two weighings represents the 
water soluble. 

Iron.—The presence of iron is readily detected by the 

- yellowish red color which it imparts to the stearate 
solutions. The proportion is usually very low, less than 
.1 per cent. In such small amounts it would have no 
effect on quality, except in so far as color is concerned. 
Traces were found in both good and poor samples, 
hence it is believed that a quantitative determination is 
unnecessary except possibly when the material is to be 
used in a white or very light-colored product. Even in 
the latter case observations of the color of solution 
alone would probably be sufficient. | 


Conclusions.—The viscosity or “body” of solutions of alumi- 
num stearate in a given solvent varies enormously for different 
samples of stearate. Comparing the results of the firmness test 
with the viscosity of xylol solutions (Table XXXVII), it ap- 
pears that the viscosity also varies with the solvent used. 
For instance, Sample No. 8, which showed a rather high yield 


ar SBh 


ALUMINUM STEARATE 


LL EE) OL OTL ET OTEN ‘IVI “SS9TIOTOD % 9S L % 8° % 918 % LS 0 all 
ad ‘Tea[ “MOTTOA AOA | = =%98'8 %¥9' I YG OT B'S II 
Vue fee ABO L)ereee late) %6'S YS v %es Ot %8'T OL 
9) ‘APNOP) YVYMOUIOG —“SS9TIOTOK) %90'9 %0'F¥ % 90° OT %6 1 6 
V ueyy ssorT ‘IVat) “MOTPOA ATOA | %1B'6 % SBE" %9'6 %6'T 8 
Wy EHD eee) ‘ApNopo ATS “SSoP1OTO) Yo LS %o8° Me 6 %E9'S L 
‘Ivapo AT[BOIJORIg 
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© PONS e0lS %o& 6 Yl % Yov Ul % 86° g 
= ‘19}} BUI papusedsns jo JuNOUIB 
9 [[eUg “Lee]O ysoulTy “Moro Bfeq | %HVE'6S Lob obs U1 ZoL& 1 v 
Al ‘% ON SB ouIvg | = %6Z'6 %o9 1 %8 Ol % 89° ¢ 
L ‘Apnop Area “AXIAL %0'6 %ov" Yov 6 %vs" 
af ‘[Bl1lo}eul popuodsns Jo yuNOUIG ; 
f eae rae ae Be at) YS L % SE" %S8' L Yoo" J 
sprepueys IP[OH JO[AX Jo ‘SUIS &G %aT aTqnyjos onpIsad 
-laupier ‘“suOryNyOS OG Ul 94vIB9}S JO SUIBIS pure “O Vv I0}8 MA UOT}IUST dINYSTOT ‘ON 
JOJAX JO AYISOOSTA Z jo Uorynjos jo souvirveddy | 
adv L 


aypunayg wnuwuny fo sajdwng fo uoynuwpey fo 877nseay—TIAXXX 


192 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


point in the firmness test, produced a solution of very low vis- 
cosity when dissolved in xylol. 

The chemical examination has not proceeded far enough to 
draw any very definite conclusions. It appears, however, that 
the percentage of water soluble matter is important since those 
samples having the highest percentage, in general yield the 
least viscous solutions. The proportion of unneutralized stearic 
acid and of aluminum oleate probably modify to a certain extent 
the physical properties. | 


SUGGESTED TENTATIVE SPECIFICATIONS FOR ALUMINUM 
STEARATE 


The aluminum stearate must be finely divided and satisfactory 
for use in the paint and varnish industry. It must be white in 
color, and contain not over 0.1% iron as FeOs. | 

Moisture.—It shall contain not more than 1.5% of moisture. 

Water Soluble.—It shall contain not more than 2. 0% of water 
soluble material. 

Water Insoluble Ash.—The ash from the water oes ma- 
terial shall be not less than 6.0%. 

Appearance of Solution.—When 2 grams of aluminum stearate 
is dissolved in 50 grams of xylol, a practically colorless and fairly 
clear solution shall be obtained. 


CHAPTER XXII. 


SUGGESTIONS FOR MAKING 
EXPOSURE TESTS ON PAINTS AND VARNISHES 


(EXPOSURE TESTS ON PAINTS) 


(a) Select a soft wood such as white pine or poplar, unless 
it is desired to get special information as to the durability of 
paints on such woods as red cedar, yellow pine, or cypress. The 


FIGURE 86 
Old panel exposure tests back of laboratory. 


latter woods are used where the penetrating properties of SVEN 
primers are being studied. 

(b) The panels used in previous tests made on a large scale 

were constructed to be 36” « 18” of three widths of siding, with 
a weather strip at the top. They were braced at the back. (See 
reports on the Atlantic City and Pittsburgh tests in early cir- 
culars of Scientific Section.) 
_ (c) When space for such panels is not available, boards 
15” x 6” X 1” of dressed lumber are used. Allow the finished 
panels at least a week’s exposure to sun and weather previous 
to painting. Then air-dry in laboratory for a week, if they are 
to be painted inside. 

(d) Always make tests in duplicate. 

(e) If panels are to be painted inside on account of bad 
weather, allow each coat to dry indoors for 24 hours and then 
place out-of-doors for a period of at least three days’ drying be- 


193 


194 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


tween coats. If possible, allow 10 days time between the coats 
for drying. The durability of any paint depends largely upon 
the period allowed for the drying of the successive coats. 

(f) If a white paint of a new formula is being tested, apply 
the paint in light tints as well as in white. Chalking of the 
white paint is not easily noticed. Chalking of light tints of the 
same paint will often be noticed by the flooding of the chalked 


FIGURE 87 


_ Type of construction used in Atlantic City, Pittsburgh, North Da- 
kota and similar test fences. Modern tests should have panels at 45° 
to aie vertical to accelerate exposure. 


oitie pigment, which is often termed “fading.” Rich cream, 
pea green, and sky blue tints are suggested. 

(g) If possible, make exposures under two or more FAtmAtic 
conditions in various parts of the country. 

(h) Expose panels facing south. If panels are (ica at an 
angle of 45° to the vertical, the tests will be accelerated about 
50%. 

(i) For metal paints, the selection of sand-blasted panels: i is 
preferred, since test panels free of loose mill scale are not easily 
obtainable. Cleaning of the surface of metal panels with benzol 
to remove grease is advisable previous to test. Metal panels 
15” < 6” and of 18 to 22 gauge are of sufficient size for a test 
if made in duplicate or triplicate. Where space is available, 
panels 24” « 36” are preferable. 

(j) Examine the tests at least every six months and record 


EXPOSURE TESTS 195 


the results on a blank form, in accordance with the standards of 
the American Society for Testing Materials, as given below. 

A. S. T. M. Method for Reporting Condition of Exposure 
Tests.—It is important that uniform, precise and relatively ac- 
curate methods for describing or measuring the character and 
amount of disintegration of paint coats be adopted. Unless such 
standards are evolved, reports made on the wearing values of 
paints by different investigators or observers cannot be intelli- 
gently or accurately compared. 

In considering the adoption of definitions for terms generally 
used in reporting condition of painted surfaces, descriptive 


« 


FIGURE 88 


Member of Educational Bureau and Inspection Committee at At- 
lantic City Panel Tests during spring of 1910. 


words now in common use have been adhered to. In addition, 
an effort has been made to assign numerical values to these 
descriptive terms with the idea of ultimately working out some 
scheme whereby paint tests may be given a definite rating. A 
great deal of study is still required in order to assign values to 
the descriptive terms, so that the final rating may not only be 


196 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


an accurate one, but that it may really represent some well- 
balanced and understandable relative measure of service value. 

Checking.—Checking describes slight breaks in the paint coat 
which do not extend through to the surface painted. This is 
reported and rated as: 


Absent... ow Re Ae a 10 
Very. ‘slightest 9 
Slight) ie le ei ls eerie eee ee {f 
Considerable... a ee 
1 


Alligatoring.—Alligatoring describes an aggravated form of 
checking. The breaks in the paint coat are wider than in check- 
ing and usually extend almost through to the surface painted. 
While the condition is seldom observed, it is advisable to include 
the term “Alligatoring’ in the list of definitions. This condi- 
tion is reported and rated same as for “checking.” 

Cracking.—Cracking describes a break which extends down 
to the surface painted. It may be a break which immediately 
extends down to the surface painted or it may be the develop- 
ment of what was first checking or alligatoring. 

‘On wood, cracking is usually parallel with the grain, although 
sometimes it is at right angles to the grain. This condition is 
reported and rated same as for “checking.” 

Flaking—Flaking describes the falling away of small pieces 
of the paint coat. This type of disintegration is generally the 
result of checking which gradually develops into cracking, end- 
ing in the crumbling of the paint coat. This condition is re- 
ported and rated same as for “checking.” 

Scaling.—Scaling describes the breaking away of pieces of 
paint of considerable size. This condition is generally the result 
of long cracks, on wood, usually parallel with the grain. This 
condition is reported and rated same as for “checking.” 

Blistering.—Blistering describes a condition where the paint 
coat is detached and raised from the surface over which it is 
applied, due to the formation of gases beneath the coating, in- 
fluenced generally by moisture behind the coating. 

The breaking of the blister results in peeling of the paint coat. 

Peeling.—Peeling describes the pulling away or falling away 
of large pieces of the paint coat from the surface to which it 
was applied. 

Peeling of paint is not the result of natural wear, but is due 


EXPOSURE TESTS 197 


to improper application or to adverse conditions at the time of 
painting, such as moisture behind the paint coat or a faulty 
application of the priming coat. 

Gloss.—Although much depends upon the nature of the coat, 
it is not.advisable to report condition of gloss after a paint has 


FIGURE 89 


Roof tests of paints and varnishes on writer’s laboratory, showing 
panels 45° to the vertical, which nearly doubles the speed of disintegra- 
tion. Also note apparatus for daily spraying panels with water, which 
also greatly increases speed of failure, thus making such tests ac-_ 
celerated roof exposure tests. . 


weathered for more than a year. The gloss which a paint had 
shortly after its application disappears in proportion to the 
chalking of the paint, and while it is possible to restore a gloss 
to a surface in some cases, by rubbing, the gloss restored is the 
result of abnormal treatment. Gloss may be reported as: | 


ree COU ee gs Oy tee 6 tC Me 10.0 

VEAP rig fC Sn SS RAG Ne a a oy Pa Sere a 9.9 to 8.0 
IBIACT AD Gm gn es. en ee es 7.9 to 6.0 
vol) Eo a I eile RNS, os Sentie Aae OS aye ane ne 5.9 to 4.0 
UI EL EME cgay 3.9. to. 2.0 
ESC TESA Ta ae ie RR ore? RT ah) END, AOR Oe 1.9 to 0.0 


198 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Chalking.—Chalking describes the reduction of the outer sur- 
face of the paint coat to a powdery substance, which may be re- 
moved by rubbing the coating with the dry finger, or a piece of 
soft, dark colored cloth, preferably black velvet. This condition 
is reported as follows: 


Absent Considerable 
Very Slight Heavy 
Slight Very Heavy 


It is a difficult matter to assign uniformly satisfactory ratings 
to the qualifying terms and, therefore, while the report should 
include the item of “chalking,” it is considered advisable to 
eliminate ratings. 

Hiding.—Hiding is judged entirely by the degree of conceal- 
ment of the surface painted. This property is frequently re- 
ferred to as “covering” which more correcly applies to the area 
over which a given amount of paint will spread. Hiding is re- 
ported as follows: 


NOG indie ches See ee 


Color.—Paints are divided into three classes, whites, tints, 
and colors. The degree of whiteness determines the character 
of report for the first class. Two things generally influence 
color; first, the hiding power, and second, chalking. Invariably 
a paint that chalks presents a better color than one that does not. 
The impression gained through the eye serves as the basis for 
report regarding the color of paint. The original appearance 
need not be considered. While all colors show a natural fading 
out, some retain a pleasing tone while others appear distinctly 
muddy or lack the brilliance shown when first applied. The 
terms used for reporting color are: 


Very Good Poor 
Good Very Poor 
Medium 


It is not considered advisable to assign rating to the descriptive 
terms. 

General Appearance.—The general appearance of painted sur- 
faces can really be determined only by viewing them from a 
distance of twenty or thirty feet, with the idea of forming an 


EXPOSURE TESTS 199 


opinion as to whether the appearance is good, which will be 
influenced by such conditions as cracking, sealing, chalking, and 
other conditions usually found in paint wear. 

Exposure Tests on Varnishes.—For making exposure tests on 
varnishes, the following suggestions will be of value. 

(a) Use a series of unfilled panels of dressed maple wood 
15” x 6” x %”. Apply three coats of the varnish to be tested, 
allowing three days for the drying of each coat. Always test 
at the same time a varnish of similar type, the durability of 
which has previously been determined by exposure. 

(b) After the first coat has been applied and dried indoors 
for three days, it should be lightly sandpapered with No. 00 
sandpaper before applying the second coat. The second and 
third coats, however, should be applied without sandpapering or 
rubbing. The backs and edges of the panels should be varnished 
with three coats of the sample but for these surfaces the details 
of application need not be adhered to, as the effects of exposure 
on these surfaces are not considered. 

(c) Three days after application of the third coat, the panels 
should be exposed out-of-doors, 45° to the vertical, facing south. 
Inspection of the varnished panels should be made every two 
weeks, and the following reported. I. When first cracks appear. 
II. When cracks appear on every square inch of surface. 
III. When varnish may be said to have perished. Differentiate 
between surface cracking and cracks that go clear to wood. 
Make inspection based on careful visual examination, not micro- 
scopic examination. If panels are in a smoky community, wash 
lightly with water and sponge previous to examination. 

(d) In the same manner, panels that have been coated with 
black, red, yellow, green or similar colored paints may be used 
for exposure of the varnish. For instance some varnishes used 
on agricultural implements that are painted in gaudy colors, 
may wear well over certain colors but not over others. Infor- 
mation of value may be secured in this manner. 

If such a test is made, it is highly important that the color 
should be ground in one standard liquid, either japan, varnish, or 
oil. It should be pointed out, however, that the effect of the 
color upon the varnish should not be stressed unless the varnish 
was going to be used over some of these colors, as for instance 
upon agricultural implements or similar articles. 


, VARNISHES AND COLORS 


EXAMINATION OF PAINTS 


200 


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201 


EXPOSURE TESTS 


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, VARNISHES AND COLORS 


WXAMINATION OF PAINTS 


202 


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EXPOSURE TESTS 203 


(e) Unless exposure tests are made in comparison with a 
standard sample of known previous exposure, or one that has 
been chosen to act as a standard in the test, then the informa- 
tion obtained is difficult to interpret. For this. reason, a stand- 
ard sample should always be included in the tests, and it should 
be taken from a container that has not been previously opened. 
Moreover, varnish exposure tests should be made on varnishes of 

like nature or which are intended for like exposure. For in- 
stance, interior varnishes which have given satisfaction for 
many years on interior surfaces would in most cases break down 
on exterior exposure in less than a month’s time. Such break- 
down would, of course, be no indication of their usefulness as 
an interior varnish. In the same way, some grades of exterior 
spar varnishes which would stand many months’ exposure out- 
side might be unsatisfactory for certain purposes inside. 

(f) Insofar as possible, exposure tests should be made with 
the varnish and the undercoats which are actually going to be 
used in practice. The use of three coats of a varnish which is 
not intended for use over itself, is, of course, incorrect. For 
instance, three eoats of an automobile finishing varnish on a 
piece of bare wood would constitute the wrong method of in- 
terpreting the real value of such varnish which is always used 
over built-up undercoats. 


Exposure Tests on Antifouling Pants.—For testing the com- 
parative resistance of compositions to the attachment of barn- 
acles, the writer has employed steel plates 18 by 24 inches and 
of about 16 gauge, provided with half-inch holes at the top. 
These plates are usually given one coat of anticorrosive and 
then one or two coats of antifouling paint. The drying time of 
the compositions is usually such that the three coats of paint can 
be applied inside of two hours’ time and the plates immediately 
immersed in salt water. The depth of immersion should be such 
that at low tide the plates will be at least two feet below the sur- 
face. They can be suspended with sister hooks attached to wires 
suspended from girders, as shown in the illustration below. The 
piling for supporting the girders should be preferably of un- 
dressed timber, as the bark on the piling resists the attacks of 
marine borers of the teredo or limnoria type for a considerable 
period of time. 

Examination of the plates should: be made every month by 


204 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


FIGURE 96 


Test racks on seacoast for submarine exposure. The writer and R. S. 
Perry, Jr., have exposed nearly a thousand plates coated with proposed 
antifouling compositions. 


FIGURE 97 
Patch test of antifouling paints on vessel. 


EXPOSURE TESTS 205 


pulling them up and studying them at the surface. The inspec- 
tion should be for barnacles of the various species, such as bala- 
nus eberneus, etc., and for the presence of worm tubes, ascidians, 
and bryozoa. The amount of corrosion on the film and the 
amount of slime-forming constituents should also be noted. As 
a rule, paints which show a slimey deposit on the surface resist 
barnacle attachment better than others. 

For exposure tests to determine the value of copper paints for 
wooden bottoms, the writer has used slats of yellow pine three 
by one inch and about fifteen feet in length. These are nailed 
to a dock extending out under the water so that the major por- 
tion of the coated area will be below water even at ebb tide. They 
are pulled up every three months and a small section sawed off 
at the bottom to determine whether any wood-boring organisms 
(teredo, limnoria, etc.) have entered through the paint or 
through abraded surfaces. 


A Sub-Committee of the A. S. T. M. on varnish exposure tests 
expects to carry on extensive tests on metal, jananned metal, 
glass and wood during 1925. A report with recommendations 
on method of test and best type of panels to use may result from 
this work. 


CHAPTER XXII. 


TESTING COLORS FOR TONE AND STRENGTH 


Generally speaking pigment colors are bought on physical 
tests rather than chemical analysis. While it is true that the 
knowledge of the exact chemical composition of a color may be 
desirable for certain uses nevertheless the value and suitability 
of colors for most purposes can be quickly determined by physi- 
cal tests for overtone and strength, and while making these tests, 
the relative oil absorption, texture, etc., can be noted. Sugges- 
tions made by A. F. Brown are included below. 

In testing for overtone and strength it is absolutely essential 
that certain fundamental principles be observed, otherwise, the 
tests of two given samples will be misleading. The common 
practice of weighing roughly a given amount of color, then 
adding a certain number of drops of oil and rubbing an indefi- 
nite length of time with a spatula is apt to result in errroneous 
conclusions. Not only is it necessary that the dry color be 
accurately weighed, but the vehicle should also be weighed. Two 
colors ground in different vehicles should never be compared, as 
different vehicles produce different effects with the same color. 
Sufficient vehicle should always be used so that when the color 
has been rubbed and applied to a strip of glass, or tin, the sur- 
face has a high gloss. In comparing the overtones of two colors, 
if it so happens that one sample has higher oil absorption than 
the other, sufficient additional oil should be used with the color 
having the higher oil absorption to produce a paste of about the 
same consistency, otherwise the comparison will be misleading. 

The amount of dry color used’in making tests depends upon 
the type of color and the oil absorption. For C. P. Blues and 
C. P. Para and Toluidine Toners 0.5 grams of color is sufficient, 
while for C. P. Chrome Greens, C. P. Chrome Yellows, C. P. 
Oranges and all reduced colors, one gram of dry color is not too 
much. The proper amount of vehicle is dependent upon the oil 
absorption and the type of vehicle used. Experience has shown 
that where colors are to be used for certain purposes such as 
enamels, tests are more comparable to factory practice if rubbed 
in a viscous non-volatile medium such as a polymerized linseed 
oil about the consistency of 00 litho varnish, instead of raw or 


206 


TESTING COLORS ; 207 


refined linseed oil. In a general way the proper proportion of 
dry color to vehicle is as follows: 


TABLE XXXVIII 


: - Polymerized Linseed Oil 
Raw Linseed Oil (00 litho varnish) 


Gram color | Gram oil | Gram color | Gram oil 
Oe sro DUCE. oa eee as 5 eS me 6 
febebara LONCYs,. ol... 3) 8 a5 8 
CP; Toluidine Toner......... 5 6 ee 8 
C. P. Chrome Green Light.... 1.0 Pri 1.0 3 
C.P. Chrome Green Medium. . 1.0 6 1.0 4 
C.P. Chrome Green Deep..... 1.0 ih 1.0 5 
C.P. Chrome Yellow......... 1.0 A 1.0 4 
C.P. Chrome Orange......... 1.0 43 1.0 3 
Reduced Chrome Greens...... 120 135 1.0 3 


In weighing, it is desirable to use balanced watch glasses 
counterbalancing the sample against the standard with which it 
is to be compared; the dry colors being first weighed and then 
the vehicle which is placed slightly away from the color. With 
a little care, no trouble will be had in transferring the mass to 
the rubbing slab. Some operators prefer to add the oil from 
a burette, each drop of raw oil being assigned a definite weight. 
Bodied oils, however, could not be accurately weighed by such a 
method. 

The materials should be very carefully transferred to the rub- 
bing slab. Plate glass about 24” x 24” that has been lightly 
sandblasted (such as can now be obtained from any chemical 
glassware supply house) serves very well as a rubbing slab, 
and a glass muller with a 214” face is about the right size. The 
color and vehicle are first mixed with a spatula until there are 
no dry particles of color, then the resultant paste rubbed with 
the glass muller a definite number of times, care being taken to 
exert the same pressure on both samples so that the relative 
development will be exactly the same. 

The number of times a color should be rubbed depends upon 
the type of color and the actual factory practice as regards 
development. In some factories colors are well ground, but in 
many ostensibly efficient plants it is surprising how little atten- 
tion is given to securing the maximum money value by complete 


208 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


development. In a general way the number of “rubs” necessary 
to secure development equivalent to average factory practice is 
as follows: 


C, Poaron: Blues. oo eee 300 times 
G, .P.* Para-Toners24 oo eee 300 times 
C.F. ‘Toluidine Toners... 3... 3 See 300 times 
C..P. Chrome’ Greens. 2. a ee eee 150 times 
C. P; Chrome “¥ ellowsic (2003.4 eee 50 times 
Reduced Colors,.all kindss.4.. 3.2 eee 50 times 
Lakes. 36g ee a a 200 times 


In rubbing, the muller should traverse a space about three 
inches wide and twelve inches long, the operator pushing the 
muller up one side and down the other side of this strip so that 
all the color particles receive the same amount of attrition every 
rub. By one rub is meant one complete movement up and down. 
In testing a color which requires twenty-five rubs the color 
should be scraped up after fifteen rubs and then rubbed another 
ten times; when testing a color requiring more than twenty-five 
rubs the color should be scraped up with a spatula after each 
twenty-five rubs. After the rubbing is completed the compari- 
son for overtone should be made by applying liberal portions 
of each color to glass or tin in juxtaposition. The larger daub 
of color the better, but in any event each daub should not be 
smaller than a half-dollar and they should be placed in juxta- 
position, care being taken that the edges just touch but do not 
overlap and that there is a well defined line of demarcation. 
After being so placed and before comparing, a wide spatula 
should be lightly drawn over both at the same time to produce 
a color surface that will be smooth and free from ridges. In 
comparing for overtone, the colors should not be examined 
through the glass. For this reason strips of tin are preferable 
to glass as it effectively prevents this practice. If the colors 
are to be used for inks, this test may be made upon bond paper. 
Observation of the stained paper when held to the light will show 
whether the color is clear, bright or muddy. 

For making strength tests, it is well to have a stock paste 
of zinc oxide in oil. Such a paste can be made by vrinding 185 
parts of zine oxide and 115 parts of OO litho oil several times 
through a roller mill. A strength test can then be quickly made 
by taking a small amount of the paste color made as outlined 
above for comparing the overtone and adding the proper amount 
of zinc oxide paste. 


TESTING COLORS 209 


‘For reduced colors a reduction of 20 to 1, 7. e., 20 parts zinc 
oxide paste to 1 part paste color, is usually sufficient but for 
C. P. colors a 100 to 1 reduction is necessary to get the proper 
idea of relative strengths. Very often two C. P. colors which 
apparently are about the same strength on a 20 to 1 reduction 
are very far apart on a 100 to 1 reduction. In making the re- 
duction test the best way is to counterbalance 100 milligrams of 
the two paste colors to be tested and then add to each, two grams 
of the paste zinc oxide. Before removing from the counter- 
balanced watch glasses mix the color with the zinc oxide, using 
a small spatula thus minimizing the loss on transferring, then 
remove from watch glass to a smooth piece of glass and mix with 
a, spatula until the color no longer streaks, which indicates that 
it is thoroughly incorporated. Never make a strength test on 
a rough glass and do not rub with a muller, as this develops 
strength that is not secured in factory practice. In the event 
that a 100 to 1 reduction is desired, take 500 milligrams of 
the first reduction, add 2 grams of zinc oxide paste and proceed 
as before. 

If it is desired to express quantitatively the tinting strength 
of the color, consider the standard color as having a tinting 
strength of 100, and then vary the amount of the standard color 
until the tints are matched. 

For example, let the amount of standard color for 100 strength test be 


0.02 g. (=A). Vary this amounts in units of 5 per cent, thus 0.019 or 
0.021. Let the amount taken to match a given strength— 8B, then 


ee. 100 
B 


equals the tinting strength of the sample to be tested. 

If the tone varies it may be difficult to make this measurement. 

The comparison for overtone should be made as soon as the 
colors have been applied to the strip of glass or tin, otherwise 
“flooding” may result in one or both samples and there will be 
no basis for comparison. 

Generally speaking, it is good practice to have separate rub- 
bing glasses for each of the four general classes of color—greens, 
yellows, blues and reds to avoid contamination of one ‘color with 
another. If one glass is used for all colors, great care must be 
exercised to insure absolute cleanliness. It is surprising, for 
instance, how little chrome green is required to off-shade a prim- 
rose yellow. Benzol 90° is probably the best liquid for cleaning 
the rubbing glasses. © 


CHAPTER XXIII. 


ROUTINE TESTING METHODS FOR SOME PHYSICAL PROP- 
ERTIES OF WHITE PIGMENTS SUCH AS ZINC OXIDE, 
LEADED ZINC AND LITHOPONE 


The following routine tests for color, brightness, smoothness, tinting 
strength and settling are contributed by the Research Laboratory of the 
New Jersey Zinc Co. 

Color—Approximately 5 grams of the sample shall be thor- 
oughly mixed with the smallest quantity of bleached linseed oil 
that will produce a smooth paste. This paste shall be spread 
on a palette of colorless plate-glass in a smooth and even layer, 
that will not transmit light and is at least 1 inch by 3 inches in 
area. 

An equal amount of the standard (or each of the standards) 
shall be prepared in the same way, care being taken to bring the 
paste to the same consistency as the sample being tested. This 
paste shall be spread in a similar manner on the palette beside 
the sample, touching it, and the two compared in diffused day- 
light. In doing so, the palette shall be tilted so that the light 
will strike the surface of the pastes at different angles and the 
under surfaces shall also be observed through the glass. 

In doubtful cases, only the sample and one standard may be 
spread on the palette at the same time, and their edges must 
touch. 

To be on-grade, the sample must be as white as the standard. 

Brightness.—Five grams of the sample and 1.20 grams of 
bleached linseed oil shall be mixed to a smooth, uniform paste. 
The oil used may be determined by dropping from a point which 
has been standardized by counting the number of drops neces- 
sary to weigh 1.20 grams. The dropping shall be at a rate not 
greater than 70 drops per minute. All the sample and all the 
oil must be thoroughly incorporated. This paste shall be spread 
on a palette of colorless paste-glass in a smooth and even layer 
that will not transmit light and is at least 1 inch by 3 inches 
in area. 

When the nature of the pigment requires more oil than above ~ 
noted, more shall be used but comparisons shall be made. only 
between samples which have a like oil-vehicle ratio. 

An equal amount of the standard shall be prepared in the 


210 


ROUTINE TESTING METHODS FOR WHITE PIGMENTS Zk 


same way. This paste shall be spread in a similar manner on 
the palette beside the sample, touching it, and the two compared 
by observing in diffused daylight the two samples by looking 
through the glass. 

In doubtful cases, only the sample and one standard may be 
spread on the palette at the same time, and their edges must 
touch. - 

To be on-grade, the sample must be equal to or better than 
the standard in brightness or brilliancy. 

Smoothness and Freedom from Specks.—Approximately 5 
grams of the sample shall be thoroughly mixed with the smallest 
quantity of bleached linseed oil that will produce a smooth paste. 
This paste shall be spread on a palette of colorless plate-glass 
in a smooth and even layer that will not transmit light and is at 
least 1 inch by 3 inches in area. 

An equal amount of the standard shall be prepared in the 
same way, care being taken to bring the paste to the same con- 
sistency as the sample being tested. This paste shall be spread 
in a similar manner on the palette beside the sample, touching 
it, and the two compared in diffused daylight. In doing so, the 
palette shall be tilted so that the light will strike the surface of 
the pastes at different angles. . 

In doubtful cases, only the sample and one standard may be 
spread on the palette at the same time, and their edges must 
touch. 

To be on-grade, the sample must contain no more granular 
or foreign matter than the standard. This is to be determined 
by the feel under the knife and the amount of noise made in 
rubbing down and by observation of the surfaces after the 
pastes have been spread on the palette. 

Tinting Strength—Five grams of the sample, 0.5 grams of 
ultramarine blue and 1.20 grams of bleached linseed oil shall be 
mixed to a smooth, uniform paste of uniform color throughout. 
The oil used may be determined by dropping from a point which 
has been standardized by counting the number of drops neces- 
sary to weigh 1.20 grams. The dropping shall be at a rate not 
greater than 70 drops per minute. The mixing shall be done 
by rubbing lightly with a spatula whose blade is not over 5 . 
inches long. All the sample, blue and oil must be thoroughly 
incorporated. This paste shall be spread on a palette of color- 
less plate-glass in a layer that will not transmit light. 


212 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


The standard shall be prepared in the same way and spread 
in a similar manner on the palette beside the sample, touching it. 

Another standard paste shall be prepared by mixing 5.5 grams 
of the standard, 0.5 grams of ultramarine blue and 1.32 grams 
of bleached linseed oil in the same way and spread in a similar 
manner on the palette beside the sample, touching it. 

In doubtful cases, only the sample and the two standards may 
be spread on the palette at the same time and the sample must 
be in contact with both standards at the edges. 

To be on-grade, the sample must not be darker than the first 
standard and not lighter than the second standard when ob- 
served through the glass. 

Settling in Water.—This test shall be made in a flat-bottomed 
glass tube of 11/16 inch diameter, 6 inches height and uniform 
bore. Twenty-seven cc. of water should fill it to a height of 
43/4, inches with an allowable plus or minus variation of 1/16 
inch. 

Five grams of the sample shall be put into the tube after the 
latter is half filled with water. The product and water shall be 
well mixed with a piece of wire about 14 or 12 gauge and the 
tube filled with water to a height of 434, inches. The wire is to 
be removed and washed off in the process of adding this water. 
The tube shall then be shaken vigorously 80 times, the thumb 
being held over the opening in the top. After shaking, it shall 
be placed in a rack so that it stands vertically and the height of 
the column of the product measured at the end of 1, 2, 3 and 
24 hours. 

An equal amount of the standard shall be treated in the 
same way. 

To be on-grade, the height of column of the sample must be 
within 10 per cent plus or minus of the height of column of the 
standard at the end of 24 hours. 


CHAPTER XXIV. 


ANALYSIS OF PAINTS AND PAINT VEHICLES 


When examining a sample of mixed paint, it is customary to 
weigh the paint and container, subsequently deducting the 
weight of the cleaned container to determine the weight per gal- 
lon. About an ounce or two of the clear liquid above the settled 
pigment can b poured off to use for analytical purposes. The 
balance of the liquid can then be poured into a large container 
and the condition of the settled pigment determined by exam- 
ining with a large spatula. The presence of granular matter, 
metallic soaps, etc., is determined. The presence of soaps precipi- 
tated out of the liquid upon the sides of the can above the set- 
tled pigment should also be looked for. The settled pigment 
should then be broken up carefully by pouring back the liquid 
and the mixture stirred to a uniform mass. For this purpose, 
it is necessary to “‘box” the paint back and forth from one large 
can to another in order to get a thoroughly uniform mixture 
for analysis. Otherwise, low results might be shown in the per- 
centage of pigment present. A small amount of the uniform 
sample of paint thus obtained, together with the small sample of 
the clear liquid originally obtained previous to boxing, can be 
used for the analytical tests. The amount of clear liquid taken 
should be figured in calculating the percentage of pigment in 
the paint. 

Composition of Liquid Part.—The vehicle or liquid portion 
of paints may contain various fixed animal, vegetable or mineral 
oils, oleo-resinous varnishes, turpentine, mineral distillates, ben- 
zol and driers. 

Percentage of Liquid by Ignition Method.—The percentage 
of vehicle in the uniform sample of paint previously obtained 
may be found by placing a weighed portion in a porcelain cru- 
cible and slowly igniting it to burn off the organic constituents. 
By carefully regulating the heat, the oil and volatile thinners 
will be slowly burned off, leaving the pigment behind, which may 
then, be weighed, calculating the vehicle by difference. This 
method is a rapid one and works well with some pigments. When 
pigments are present which show an appreciable loss on igni- 
tion, or blacks or blues, this method is not to be relied upon. 


213 


214 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Percentage of Liquid by Extraction Methods.—Another good 
method of separating the vehicle from a paint is to place a por- 
tion in a large tube, adding a considerable quantity of benzol, 
petroleum ether, or that portion of gasoline distilling below 120° 
C., subsequently centrifuging. Pigments which settle slowly 
are thrown down very rapidly by this method. The process is 
repeated three or four times in order thoroughly to free the pig- 
ment from oil. After drying, the pigment is weighed and the 
percentage of vehicle determined by difference. In case a cen- 
trifuge is not available, the vehicle of many paints may be sepa- 
rated by simply shaking a portion of the paint in a long test- 
tube with benzol, allowing the pigment to settle, repeating the 
extraction until the oil is thoroughly removed. 

Some operators have from time to time used Soxhlet extractor 
for the determination of the vehicle of a paint. This method is 
rather slow and does not always give satisfactory results. 

It must be remembered that no method of extraction of the 
oil from a paint will give absolute results. The last traces of 
oil cannot be removed from the pigment which is probably 
due to the fact that many pigments such as lead and zinc 
react with the oil, producing small quantities of insoluble soaps 
which are not completely dissolved by the solvent. | 

In the extraction of paints, the choice of a solvent is impor- 
tant. When benzol (90°) is not available, it may be replaced 
by gasoline that has been redistilled, using the light fraction 
coming over below 120° C. This cannot be used, however, when 
varnish resins other than rosin are present, as they are insoluble 
therein. A good solvent often used by the writer may be made 
of Ethyl Ether 10 Volumes, Benzol 6 Volumes, Methyl Alcohol 
4 Volumes and Acetone 1 Volume. 

There are some pigments which by reason of their low specific 
gravity, colloidal nature or partial solubility can never be com- 
pletely separated from oil, either by settling, centrifuging or 
extraction. Of these the most commonly met with are lamp- 
black and other forms of carbon, zinc oxide and Prussian blue. 
Colloidal pigments such as zine oxide are very troublesome in 
this respect. When these pigments, however, are present in a 
paint in considerable percentage, the difficulty of their sepa- 
ration may be avoided by adding to the paint three or four 
times its volume of fuller’s earth, diluting the mixture in a large 
test-tube with gasoline or petroleum ether and either centrifug- 


ANALYSIS OF PAINT VEHICLES 215 


ing or placing in a rack to settle. The fuller’s earth carries 
down the colloidal pigments and the separation is sharp and easy. 
This method, of course, is simply used to extract the vehicle 
present. The pigment resulting from the separation cannot be 
used for analysis on account of admixture with the fuller’s 
earth. | 

In some cases the pigments in paste colors made of lamp- 
black and Prussian blue cannot be separated from the vehicle 
portion. The amount of Prussian blue present, however, may 
be determined by making a Kjeldahl-Gunning determination on 
a portion of the entire paint, multiplying the nitrogen found by 
4.4. For the determination of the lampblack present, a portion 
of the entire paint may be boiled with an excess of alcoholic 
potash until all of the oil is saponified. The mixture is then 
decanted through a filter and washed, first with hot alcohol and 
then with hot water. This affords a very good separation of the 
vehicle from the pigment of such paints. By this method, the 
Prussian blue which may be present is partially destroyed, the 
iron content remaining admixed with the black pigment on the 
filter. 

Separation of Vehicle Components.—When possible, it is ad- 
visable to determine the constituents of the vehicle upon that 
sample that has been removed from the top of the settled can 
of paint. A weighed portion of this vehicle may be placed in a 
tared flask and attached to a Liebig condenser. Heating to 
180° C. or lower will drive off nearly all the volatile constitu- 
ents. The composition of the distillate may be determined by 
the methods given under the Examination of Turpentine. (See 
specifications in back of volume.) A portion of the residue in 
the flask, which consists of oils, driers, gums, etc., may be 
transferred to a crucible and ignited. The residue may then be 
weighed and calculated to ash. The ash should be analyzed for 
lead, manganese and other driers. 

Another portion of the original vehicle may be evaporated 
in an atmosphere of CO, (prevents oxidation) to remove the 
volatile constituents. A portion of the oil residue may then be ex- 
amined for iodine number and other constants. In some in- 
stances it would be advisable to make a saponification and ex- 
traction of the fatty acids from this residue, determining the 
iodine number on the fatty acids. 

Water.—For a direct determination of the percentage of 


216 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


water in a paint, the analyst may place a weighed quantity (ap- 
proximately 100 grams) of the paint in a metal still, mixing 
it with an equal quantity of sand. Distillation will drive off 
the water and other volatile constituents which will separate 
into two layers in the graduate, or if no metal still is available, 
a direct distillation with Toluol (water saturated) may be re- 
sorted to. 

Direct Distillation for Volatiles—For a direct determination 
of the volatile constituents in a paint, a.sample may be distilled 
in vacuo. This is-easily managed wherever a vacuum pump is 
available and avoids the necessity of overheating the oil. When 
distilling by this method, a sample of the clear vehicle should 
not be heated above 150° C. and neither should the solvent be 
volatilized in such a way as to allow the oil to be in contact with 
air, as it will oxidize rapidly while warm and its iodine number 
be very much lowered. 

The following standard method for volatile, which is Aer 
convenient and accurate, may be used in any case and particu- 
larly where it is difficult to secure sufficient clear vehicle for 
distillation. 

Approximately 1.5 grams varnish or 3 to 5 grams of jaint 
are weighed by difference from a stoppered vial into a weighed 
shallow flat-bottom metal dish (ordinary friction top lid) 8 
c.m. in diameter. The dish is heated in a well ventilated air 
oven at 105° to 110° C. until no further loss occurs, generally 
3 hours. Loss is considered volatile thinner. In paints, any 
water present, as separately determined, must be allowed for. 

Detection of Resinates—To determine whether the drier in 
a paint is of the resinate type or linoleate type, a few drops 
of the oil vehicle may be mixed on a porcelain plate with one 
or two drops of acetic anhydride, subsequently adding a drop 
of sulphuric acid. Upon the addition of the sulphuric acid, a 
flash of purple color, turning to dark brown, will be shown 
where rosin is present. If rosin should be present in the vehicle 
to a considerable extent, the oil will have a very high acid num- 
ber. The approximate percentage of rosin present may be de- 
termined by shaking a portion of the vehicle with 95 per cent 
alcohol in a separatory funnel, subsequently separating the al- 
coholic extract, evaporating and weighing the residue. 

Detection of Various Oils —Chinese wood oil may be detected 
in the vehicle by mixing the oil with an equal volume of a satu- 


a) a 


ANALYSIS OF PAINT VEHICLES 217 


rated solution of iodine in petroleum ether, allowing the mix- 
ture to stand in direct sunlight. Under these conditions, a 
peculiar, insoluble, spongy polymer of one of the fatty acids of 
Chinese wood oil is shown. Fish oil can usually be detected by 
its odor and the dark red color during saponification. The pres- 
ence of soya bean and other vegetable oils is in some cases diffi- 
cult to detect. The iodine numbers of these oils, however, are 
all lower than that of linseed oil. It must be remembered, how- 
ever, that the iodine number of boiled linseed oil is lower than 
that of raw oil and that the iodine number of oils extracted 
from many paints is usually lower than shown by the original 
oil. In the presence of considerable quantities of drier, it is 
always advisable to extract the fatty acids from oil and make 
the iodine determination upon them. Determination of hexa- 
bromides gives best information as to type of oil present. 

The distillate from the paint vehicle may consist of turpen- 
tine, mineral distillates, benzol and similar solvents. The pres- 
ence of benzol is readily detected by adding a few drops of the 
distillate to a small quantity of a mixture of concentrated nitric 
and sulphuric acids. Upon heating this mixture, the character- 
istic odor of nitro-benzol will be recognized if benzol is pres- 
ent. Mineral distillates from petroleum are easily detected by 
the polymerization method given under Turpentine Specifica- 
tions. 


CHAPTER XXV. 


ANALYSIS OF PAINT OILS 


Although linseed oil is used to the greatest extent in paints, 
some other oils occasionally find application in the manufacture 
of special paints. The following have been used for this pur- 
pose: soya bean oil, perilla oil, corn oil, cottonseed oil, sun- 
fiower oil, lumbang oil and similar vegetable oils; menhaden oil, 
whale oil, herring: oil, and similar marine animal oils of rela- 
tively high iodine number. 

Constants found on oils examined in the writer’s laboratory 
are given in Table XX XIX. 

There are given below methods for the analysis of linseed 
oil, in accordance with the latest practice developed by the 
U. S. Government Interdepartmental Committee on standardi- 
zation of paint specifications and the American Society for Test- 
ing Materials. These methods may be followed in examining 
any of the other oils mentioned above, except for iodine value 
on those of the aleurites genus. 


ANALYSIS OF LINSEED AND SIMILAR OILS 


Solutions Required.—The following reagents will be required: 

Acetone that will pass the specification of the United States 
Pharmacopeeia. 

Acid Calcium Chloride Solution.—Saturate with calcium 
chloride a mixture of 90 parts water and 10 parts HCl (sp. gr. — 
15185 

Standard Sodium Thiosulfate Solution.—Dissolve pure sodium 
thiosulfate in distilled water that has been well boiled to free 
it from carbon dioxide in the proportion so that 24.83 g. 
crystallized sodium thiosulphate will be present in 1000 cc. of 
the solution. It is best to let this solution stand for about two 
weeks before standardizing. Standardize with pure resublimed 
lodine. (See Treadwell-Hall, Analytical Chemistry, Vol. II, 
third edition, p. 646.) This solution will be approximately 
N/10 and it is best to leave it as it is after determining its ex- 
act iodine value, rather than to attempt to adjust it to exactly 
N/10 strength. Preserve in a stock bottle with a guard tube 
filled with soda lime. 

Starch Solution.—Stir up 2 or 3 g. of potato starch or 5 


218 


ANALYSIS OF PAINT OILS 219 


TaBLE XXXIX—Oils Examined in Writer’s Laboratory 


se S 
e ep | ae 
Oil. Species. & co iag Orcs “s 
o Sone eet ne 
& se es eee 
‘S Se Bio 
D Zi les ON 
R A <a | 
Ciivinmes. © oe s,s). Sa iarahe. scares 3 196.3} 192.2 1.4885 
| Hispanica 
orn ee nae oa Fs Oe a ee 190.1] 4 1.4800 
Mays 
Cottonseed....... Gossipium...... 194.3 1.4720 
Herbaceum 
Hempseed....... Cannabis....... 1911) 3 1.4822 
Sativa 
Kapok Seed......| HEriodendron.... POG VR tee ie ay 2, 
Anfractuosum 
Linseed (Boiled). .| Linum......... 187. | 2. 1.4895 | = 
Usitatissimum ss 
Linseed (Heavy | Linum......... 189. | 2. 1.4966 q 
Bodied) Usitatissimum es} 
Linseed (Lithogra-| Linum......... 199. | 2. 1.4978 = 
graphic). Usitatissimum = 
Linseed (Raw)...| Linum......... 191. }-2: 1.4800 ey 
' | Usitatissimum ce 
CPCI oo cde hee Conepia........ TSW eS 4c] ee > 
Grandifolia A. 
Palo Maria...... Calophyllum.... 193. |46. 1.4743 -) 
Inophyllum TD 
Bendis ta. 3. Periilay. oy 0s 5: 188. | 2.0 | 1.4874| & 
Ocimoides . s 
Poppyseed....... Papaver ...... - A Le Vl ee he aed one neg es O 
Somniterrum = 
Raisinseed (Grape-|.....-.--+-+++-- 198-2 |-475-| 1.471041 
seed). es 
ORIEL OTL 9 alae PIS ee ws ees SBA Osada tor 
Palustris 
Rubberseed...... le Vetin eae 5 ou: 10380 (50 20M Seen ae 
Brasiliensis 
SeOESAMO- gels. +: Sesamum....... LOO Vel ere he 
Orientale & In- 
dicum 
Soya Bean....... SO) ok eee Oe ne 189. | 2. 1.4813 
‘Hispida 
Sunflower..... Helianthus..... 189.3] 7 1.4796 
Annus 
umbang:..../:5 Aleurites....... 192.0) 1. 1.4770 
(Candlenut). Moluccana 
Lumbang (Soft). .| Aleurites....... 194.0) 4. 1.4929 
Trisperma ~ 
Peanit va... s- « Nera OPUS no tagtte bate ee 193.0} 2. 1.4790 Z, 
Hypogaea = 
Tung (American) .| Aleurites....... 194.6 1.5170 
Fordii o 
Tung (Chinese)...| Aleurites....... 192.0} 4 1.5170 te 
Fordiu ce 
POM EATAIE Gide jes ol eae: Juglans Panes 19g 0L ee 1.4770 
Regia 
Wood (Japanese) .| Aleurites....... 193.2 1.5080 


Cordata 


— ee | 


220 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


TABLE XXXIX—Continued—Oils Examined in Writer's Laboratory 


is 5 é 
ay 2 r=| P rs 
> 2 iS) oO < 
© z ees 2 = 
Oil. Species. e) Zt g3 5 ev 
= os | | Z, ay 
MOO) os 6 > 20 
Sisie| Ba | 24 | Z Hie 
Pidiis| SO] & at, coe 
Na|a 2 
Channel Cathsiix. is ve) .923 | 123.0) 192.0/10.9 | 1.4741 
Pur Beak oe AF PROCGL Ae oe .926 |-132.4) 182.4) 90 eae 
Vitulina Ete. 
Grayish iy, ces ee eee ee .916 | 185.7; 180.1) 2.0 | 1.47038 | — 
Menhaden....... Alosa Menhaden | .932 | 158.0] 187.0) 3.9 | 1.4850 = 
(Brevoortia Tyr- me 
ranis) _ 
Salmoty.cc eee Salmo. citi .927 | 159.0} 183.0] 9.8 | 1.4788 | 4 
Salar & 
Sarilines (4. 0 wie Co OoMIpen ste ee .919 | 134.6) 177.3]10.4 | 1.4800 | = 
Sardinus 4 
SUEELT Rewie “eee ke cane ee Bs a Be vas oe ee .910 | 132-8} 158.9] 5.2 | 1.4815 z 
Shark Liver...... Borealis #2 .922 | 135.9] 62.2) 1.3 | 1.4708 > 
Scymnus es Th 
Skate Liver...... PUUAtNE es .932 | 151.6) 179.9) 1.8 1 bavi2 aS 
Vulvaris = 
Une Ah oP ens Uh keer ie .9383 | 184:0) 190.0) > [at ee 2) 
Whale, =... os...) Go Baloenas. =... 924) 14s 7 ee 9.2.1 | 48200) = 
Yellow Tailfish...| Seriola......... .932 | 180°0; 190.0) eee 


Dorsalis 


—VWvVUuHRuRHexexeyeoooo>> qq eee 


g. soluble starch with 100 ce. of 1 per cent salicylic acid solution, 
add 300 to 400 cc. boiling water, and boil the mixture until the 
Starch is practically dissolved. Dilute to 1 liter. 

Potassium Iodide Solution—Dissolve 150. g. of potassium 
iodide free from iodate in distilled water and dilute to 1000 cc. 

Hanus Solution.—Dissolve 13.2 g. of iodine in 1000 cc. of 
glacial acetic acid (99.5 per cent) that will not reduce chromic 
acid. Add enough bromine to double the halogen content, de- 
termined by titration (3 cc. of bromine is about the proper 
amount). The iodine may be dissolved by the aid of heat, but 
the solution should be cold when the bromine is added. 

Standard Sodium Hydroxide Solution.—Prepare a stock con- 
centrated solution of sodium hydroxide by dissolving NaOH 
in water in the proportion of 200 g. NaOH to 200 cc. water. 
Allow this solution to cool and settle in a stoppered bottle for 
several days. Decant the clear liquid from the precipitate of 
sodium carbonate into another clean bottle. Add clear barium 
hydroxide solution until no further precipitate forms. Again 
allow to settle until clear. Draw off about 175 cc. and dilute to 


Tee ar a ey 


ANALYSIS OF PAINT OILS 221 


10 liters with freshly boiled distilled water. Preserve in a stock 
bottle provided with'a large guard tube filled with soda lime. 
Determine the exact strength by titrating against pure benzoic 
acid (C,H.COOH) using phenolphthalein as indicator. (See 
Bureau of Standards Scientific Paper No. 183.) This solution 
will be approximately N/4, but do not attempt to adjust it to 
any exact value. Determine its exact strength and make proper 
corrections in using it. ie 

Alcoholic Sodium Hydroxide Solution—Dissolve pure NaOH 
in 95 per cent ethyl alcohol in the proportion of about 22 g. per 
1000 ce. Let stand in a stoppered bottle. Decant the clear 
liquid into another bottle, and keep well stoppered. This solu- 
tion should be colorless or only slightly yellow when used; it 
will keep colorless longer if the alcohol is previously treated 
with NaOH (about 80 g. to 1000 cc.), kept at about 50° C. for 
15 days, and then distilled. For an alternate method see Jour- 
nal, American Chemical Society, 1906, p. 395. 

Half Normal Sulfuric Acid Solution.—Add about 15 ce. 
H.SO, (sp. gr. 1.84) to distilled water, cool and dilute to 1000 
ec. Determine the exact strength by titrating against freshly 
standardized NaOH or by any other accurate method. Hither 
adjust to exactly N/2 strength or leave as originally made, ap- 
plying appropriate correction. 

Methods.—The oil shall be tested in accordance with the fol- 
‘lowing methods: 

General.—The laboratory sample shall be thoroughly mixed 
‘by shaking, stirring, or pouring from one vessel to another and 
the samples for the individual tests taken from this thoroughly 
mixed sample. 

Loss on Heating at 105 to 110° C.—Place 10 g. of the oil in 
an accurately weighed 200 cc. Erlenmeyer flask; weigh. Heat 
in an oven at a temperature between 105 and 110° C. for 30 
minutes; cool and weigh. Calculate the percentage loss. This 
determination shall be made in a current of dry carbon diox- 
ide gas. 

Foots.—With all materials at a temperature between 20 and 
27° C., mix, by shaking in a stoppered flask for exactly one 
minute, 25 cc. of the well-shaken sample of oil, 25 ec. of acetone 
and 10 cc. of the acid calcium chloride solution. Transfer the 
mixture to a burette where settling can take place for 24 hours. 
The temperature during this period should be between 20 and 
ete O 


222 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


The volume of the stratum lying between the clear calcium 
chloride solution and the clear acetone and oil mixture is read 
in tenths of a cubic centimeter or a fraction thereof. This 
reading multiplied by four expresses the amount of foots present 
as percentage by volume of the oil taken. 

Specific Gravity—Use a pyknometer accurately standardized 
and having a capacity of at least 25 cc., or any other equally 
accurate method, making the test 15.5° C., water being 1 at 
T5.baG, 

Acid Number.—Weigh from 5 to 10 g. of the oil. Transfer 
to a 300 cc. Erlenmeyer flask. Add 50 cc. of neutral 95 per 
cent ethyl alcohol. Put a condenser loop inside the neck of the 
flask. Heat on a steam bath for 30 minutes. Cool and add 
phenophthalein indicator. Titrate to a faint permanent pink 
color with the standard sodium hydroxide solution. Calculate 
the acid number (milligrams KOH per gram of oil). 

Saponification Number.—Weigh about 2 g. of the oil in a 300 
ec. Erlenmeyer flask. Add 25 cc. alcoholic sodium hydroxide 
solution. Put a condenser loop inside the neck of the flask and 
heat on the steam bath for one hour. Cool, add phenolph- 
thalein as indicator, and titrate with N/2 H;SO,. Run two 
blanks with the alcoholic sodium hydroxide solution. These 
should check within 0.1 cc. N/2 H,SO,. From the difference 
between the number of cubic centimeters of N/2 H,SO, required 
for the blank and for the determination, calculate the saponifi- 
cation number (milligrams KOH required for 1 g. of the oil). 

~ Unsaponifiable Matter.—Weigh 8 to 10 g. of the oil. Trans- 
fer to a 250-cc. long-neck flask. Add 5 ec. of strong solution 
of sodium hydroxide (equal weights of NaOH and H,O), and 
50 ce. 95 per cent ethyl alcohol. Put a condenser loop inside 
the neck of the flask and boil for two hours. Occasionally agi- 
tate the flask to break up the liquid but do not project the liquid 
onto the sides of the flask. At the end of two hours remove the 
condenser and allow the liquid to boil down to about 25 cc. 

Transfer to a 500-cc. glass-stoppered separatory funnel, rins- 
ing with water. Dilute with water to 250 cc., and add 100 cc. 
redistilled ether. Stopper and shake for one minute. Let stand 
until the two layers separate sharp and clear. Draw all but one 
or two drops of the aqueous layer into a second 500-cc. separa- 
tory funnel and repeat the process using 60 cc. of ether. After 
thorough separation draw off the aqueous solution into a 400-ce. 


ANALYSIS OF PAINT OILS 223 


beaker, then the ether solution into the first separatory funnel, 
rinsing down with a little water. Return the aqueous solution 
to the second separatory funnel and shake out again with 60 cc. 
of ether in a similar manner, finally drawing the aqueous solu- 
tion into the beaker and rinsing the ether into the first separa- 
tory funnel. 

Shake the combined ether solution with the accumulated water 
rinsings and let the layers separate sharp and clear. Draw off 
the water and add it to the main aqueous solution. Shake the 
ether solution with two portions of water (about 25 cc. each). 
Add these to the main water solution. 

Swirl the separatory funnel so as to bring the last drops of 
water down to the stopcock, and draw off until the ether solu- 
tion just fills the bore of the stopcock. Wipe out the stem of the 
separatory funnel with a bit of cotton on a wire. Draw the ether 
solution (portionwise if necessary) into a 250-cc. flask and distill 
off. While still hot, drain the flask into a small weighed beaker, 
rinsing with a little ether. Evaporate this ether, cool and 
weigh. 

Hanus Iodine Number.—Place a small quantity of the sample 
in a small weighing burette or beaker. Weigh accurately. 
Transfer by dropping about 0.15 g. (0.10 to 0.20 g.) to a 500-cc. 
bottle having a well-ground glass stopper, or an Erlenmeyer 
flask having a specially flanged neck for the iodine test. Re- 
weigh the burette or beaker and determine the amount of sam- 
ple used. Add 10 cc. of chloroform. Whirl the bottle to dis- 
solve the sample. Add 10 cc. of chloroform to each of two 
empty bottles like that used for the sample. Add to each bot- 
tle 25 cc. of the Hanus solution and let stand with occasional 
_ shaking for one-half hour. Add 10 cc. of the 15 per cent potas- 
sium iodide solution and 100 cc. of water, and titrate with 
standard sodium thiosulfate using starch as indicator. The 
titrations on the two blank tests should agree within 0.1 cc. 
From the difference between the average of the blank titration 
and the titration on the samples and the iodine value of the 
thiosulfate solution, calculate the iodine number of the sam- 
ples tested. (Iodine number is centigrams of iodine to 1 g. of 
sample.) 


Note.—The unsaponifiable oil from adulterated drying oils is volatile and 
will evaporate on long heating. Therefore heat the beaker on a warm 
plate, occasionally blowing out with a current of dry air. Discontinue 
heating as soon as the odor of ether is gone. 


224 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Color.—Use Gardner-Holdt Color Meter or prepare a fresh 
solution of pure potassium bichromate in pure colorless H,SO, 
(sp. gr. 1.84). This solution should be in the proportion of 
1.0 g. potassium bichromate to 100 cc. (184.0 g.) H:sSO: Place 
the oil and ‘colored solution in separate thin-walled, clear glass 
tubes of the same diameter (1 to 2 ecm.) to a depth of not less 
than 2.5 em. and compare the depths of color by looking trans- 
versely through the columns of liquid by transmitted light. 


HEXABROMIDE TEST FOR DETERMINING PURITY OF LINSEED OIL 


The determination of the hexabromide value of linseed oil is 
probably the only method whereby adulteration with small 
amounts (5 per cent or greater) of soya bean or some similar 
oil can be detected. This test shows the percentage of ether- 
insoluble bromides which can be formed from the mixed fatty 
acids of a given sample of linseed oil. 

It has been found that the Steele-Washburn method for hexa- 
bromides yields a fairly constant figure of 46% for unadulter- 
ated commercial oils. 

Soya bean oil has been found to yield not over 6% of hexa- 
bromides, while cottonseed oil shows a zero yield. 

The calculation given below will indicate how an addition of 
10% soya bean oil to linseed oil will not lower the iodine value 
Folow the allowable minimum but will lower the hexabromide 
value to a marked degree: 

Assume a linseed oil with iodine number of 185 tu be adulter- 
ated with 10% of soya bean oil, iodine value of 130. 

: Then: 90 X 185 = 166.5 
10 130 = 30 


Iodine number of mixture = 179.5 
Assume that the same linseed oil has a hexabromide yield of 
46% while the soya bean oil yields 6% of hexabromides. 


Then: 90 xk 46 = 41.4 
10X 6= 6 


Hexabromide yield of mixture = 42.0 


A hexabromide yield of 42.0% would be much lower than any 
normal linseed oil and would indicate adulteration, while an 
iodine number of 179.5 would not indicate adulteration. 

The two methods (Steele and Washburn or Bailey’s modifica- 
tion thereof) by which the hexabromide test may be made, are 


ANALYSIS OF PAINT OILS 225 


given below. The Bailey modification differs from the Steele 
and Washburn method in that an acetic acid-bromide solution 
is used instead of a chloroform-bromide solution. The Bailey 
modification also entirely eliminates the use of chloroform from 
the reaction mixture and does not require “amylene” or other 
reagent for removing the excess of bromide after the bromina- 
tion of the fatty acids. The Bailey modification, however, re- 
quires the precipitated hexabromides to first stand over night in 
an ice chest instead of immediate washing. 


STEELE AND WASHBURN METHOD 


A. Preparation of Reagents. 

The following reagents are necessary: 

1. Chloroform.—Shake ordinary U. S. P. chloroform with 
Several portions of water to wash out all the alcohol. Dry the 
product with granulated anhydrous calcium chloride over night 
in order to remove all traces of water. Decant from the cal- 
cium chloride and distil. Add to the distillate 3 cc. of absolute 
ethyl alcohol for every 100 cc. of chloroform. Keep in a stop- 
pered brown bottle. 

2. Bromide Solution.—Mix one part ne volume of C. P. bro- 
mine* with two parts by volume of chloroform, prepared as 
above. This solution must be made up fresh each day because 
it deteriorates upon standing. 

3. Wash Ether.—Shake ordinary ethyl ether with ten per 
cent of its volume of ice cold distilled water. Separate and re- 
peat the washing three times. Dry the washed ether with fused 
calcium chloride overnight. Decant the ether through a folded 
filter into another flask and add thin slices of sodium. Warm 
gently on a steam bath under a reflux condenser until the evolu- 
tion of gas by action of the sodium has practically ceased and 
bits of freshly cut sodium remain bright in the ether. Distil 
the ether into a dry bottle and add an excess (at least three 
grams per liter) of finely powdered hexabromide of the fatty 
acids of linseed oil previously prepared. If no hexabromide is 
on hand from previous determinations it may be easily prepared 
as follows: In a centrifuge tube dissolve about 5 grams of the 
fatty acids of linseed oil in 15 to 20 ce. of chloroform. Place 


* The authors have observed that samples of bromine marked “C. P.” 
often contain considerable amounts of non-volatile material. All bromine 
which is used must be redistilled unless it is found that 5 gms. leave no 
weighable residue upon evaporation. 


226 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


the tube in a freezing mixture and add slowly with shaking, 
bromine solution until a slight red color is permanent. Add a 
few drops of amylene to take up excess of bromine. Whirl in 
a centrifuge until the precipitate has settled and then pour off 
the chloroform. Rub up the precipitate with 20 cc. of cold 
absolute ether, whirl in a centrifuge and pour off the wash 
ether. Repeat the washing with 3 more 20 cc. portions of ether. 
After drying, the hexabromide is pure enough for the prepara- 
tion of wash ether. Shake at intervals for two or three hours 
or allow the mixture to stand over night. Then place the bottle 
in ice water so that the ether solution will be at zero or not 
about 2° C. for three hours. Decant the ether solution rapidly 
through a folded filter into a dry bottle and keep tightly corked 
in order to prevent loss of ether by evaporation. 

4. Amylene.—This material may be purchased from the East- 
man Kodak Company. It is one of the organic chemicals pre- 
pared in the laboratory of the University of Illinois. It may be 
prepared in small quantities from amyl alcohol by the method 
of Adams, Jour. Am. Chem. Soc., 1918, page 1950. 

B. Preparation of the Fatty Acids. 

Weigh approximately 50 grams of linseed oil into a 114 liter 
Florence flask, and add 40 cc. NaOH solution (sp. gr. 1.4) and 
AQ ec. of alcohol. Place the mixture on a steam bath and heat 
for about 14 hour. Add 1 liter of hot distilled water and insert 
into the neck of the flask a 2-hole rubber stopper carrying a 
tube which projects into the flask so that its end is slightly 
above the liquid, and pass a stream of CO, through the tube 
- into the flask. The soap mixture may then be heated, to re- 
move the alcohol, either over a free flame or on the steam bath. 
If the free flame is used, a capillary “boiler” must be placed 
in the liquid, since otherwise the soap solution will bump badly. 
If excessive foaming takes place the current of CO, should be 
increased until it is strong enough to break up the foam. If 
the solution is heated on the steam bath, usually about 2 or 3 
hours is required to remove the alcohol, while if it is boiled over 
a free flame, one-half hour is usually sufficient. After the 
alcohol has been removed, cool the soap solution and acidify 
with dilute HCl (1-1). Insert a 3-hole rubber stopper, carry- 
ing two glass tubes arranged as for a wash bottle, leaving the 
third hole in the stopper open for an outlet for the CO,. The 
inlet tube should extend to just above the layer of fatty acids, 


ANALYSIS OF PAINT OILS 227 


and the outlet tube should extend to the bottom of the flask. It 
is essential that the outlet tube should not extend down more 
than an inch or two outside of the flask, as otherwise siphoning 
would take place, causing the liquid to boil inside the tube. 

Pass a stream of CO, through the system, and boil gently, 
uSing a capillary boiler to prevent bumping, until the layer of 
fatty acids is clear. Plug the hole in the stopper which acts as 
an outlet for the CO,. The lower layer will be forced out 
through the outlet tube by the pressure of the CO,. In this 
manner remove as much water as possible without losing any of 
the fatty acids, then remove the stopper and add about 500 cc. 
of hot distilled water, shake thoroughly so that the fatty acids 
are well washed, allow the fatty acids to separate and siphon off 
the wash water as before. Repeat the washing until the wash 
water does not give an acid reaction with methyl orange. Be- 
fore removing the last washing, insert a capillary boiler and 
boil gently until the fatty acid layer is clear. After the last 
washing, remove the stopper and suck up with a pipette the 
last few globules of water. Filter the hot fatty acids through 
a folded filter under an evacuated bell jar and keep in a well 
stoppered bottle. 

C. Preparation of Hexabromides. 

Weigh accurately in a weighed centrifuge tube (approxi- 
mately 614 inches long by 1 inch in diameter) 1.00 gram (pius 
or minus 0.05 gram) of linseed fatty acids, prepared as given 
above. Dissolve in 10 ec. of chloroform and place the tube in a 
freezing mixture kept as near—5° C. as possible, made by adding 
a little dilute hydrochloric acid to finely cracked ice. Add bro- 
mine solution from a burette at the rate of one or two drops per 
second, shaking the tube well during the addition. At first the 
bromine color will be rapidly discharged, but later the mixture 
will assume a permanent orange color indicating a slight excess 
of bromine. For most fatty acids of linseed oil about 1 cc. of 
the bromine solution will be found necessary to give the orange 
color. At this point run in rapidly 0.5 ce. more of the bromine 
solution, shake well, and allow the tube to stand in the ice mix- 
ture for ten minutes. Remove the tube from the freezing bath 
and add amylene drop by drop with shaking until the bromine 
color has entirely disappeared. Usually five to six drops of 
amylene are sufficient, but a slight excess does no harm. The 
addition of bromine solution must never be done in direct sun- 
light. 


998 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Attach the tube to a good water vacuum pump (one which 
will indicate a pressure not greater than 40 mm. of mercury) 
by means of a new one-hole rubber stopper. Evaporate the 
chloroform in a vacuum, warming the tube in water at 50 to 
60° C. to hasten evaporation. The tube must be constantly 
shaken to prevent bumping of the chloroform. Towards the end 
of the evaporation, when the contents of the tube become more 
viscous, rotate and tilt the tube so that the oil will flow about 
half way up the sides and thus present more surface for evap- 
oration. When practically all the chloroform has been evap- 
orated, place the tube in a bath at 55 to 60° C. for fifteen min- 
utes, keeping the suction on. 

Detach from the pump and place the tube in a bath of finely 
cracked ice and water. When the tube is cold pour down its 
sides 20 cc. of cold wash ether, as prepared above. The wash 
ether should have been previously placed in four corked test 
tubes graduated at 20 cc. by a file mark and kept at 0° C. in an 
ice bath. Thoroughly stir and rub up the bromide mixture 
with a rod, breaking up all the lumps. Return the tube to the 
ice bath for two minutes and then whirl in a centrifuge until 
the precipitate has settled into a hard cake and the supernatant 
liquid is clear. Return the tube to the ice bath for two min- 
utes and then pour off the wash ether, making sure that no solid 
material is lost. Repeat the washing of the hexabromide pre- 
cipitate three times in exactly the same way, using three 20 cc. 
portions of ice-cold wash ether and rubbing up the precipitate 
thoroughly each time. Use a weighed stirring rod and wash the 
precipitate adhering to the rod into the tube with the wash 
ether at each washing of the hexabromide. Afterwards ary 
and weigh the rod plus the slight coating of precipitate and add 
the weight of material on the rod to the weight of the main 
portion of hexabromide. After the fourth ether washing has 
been poured off, carefully incline and tap the tube and spread 
the hexabromide precipitate part way up the sides. Warm the 
tube in water at 50 to 60° C. until most of the ether has evap- 
orated. Attach to the suction pump and place the tube in a 
bath at 60 to 70° C. for fifteen minutes. Detach the tube from 
the pump, cool in cold water to room temperature, wipe dry 
with a towel and weigh at once. Dry the tube to constant 
weight in an oven at 100-110° C. The total weight of the pre- 
cipitate times 100 divided by the weight of fatty acids taken, 


ANALYSIS OF PAINT OILS 229 


gives the hexabromide percentage. The hexabromide should dry 
pure white. 

Special Precautions: 

1. Have the chloroform dry and adjust its alcohol content to 
three per cent. 

2. Make sure that all the chloroform is evaporated from the 
impure hexabromide before adding wash ether. This will be 
accomplished if the water pump indicates a pressure not greater 
than 30-40 mm. and the tube is heated in the bath at 60° C. for 

two-thirds of its length. 

3. Make sure that the wash ether is anhydrous and free from 
alcohol and that it is saturated with hexabromide at 0° C. Un- 
less the wash ether is allowed to stand at 0° C. for a sufficient 
length of time before filtering off excess hexabromide, it will 
be super-saturated at 0° C. and will give high results. Care 
Should be taken to prevent appreciable loss of ether by evap- 
oration; it is well to cool the stock bottle of wash ether on hot 
days before uncorking. 

4. Make sure that the centrifuge tube containing hexabro- 
mide and the wash ether are kept as near 0° C. as possible dur- 
ing the process of washing. The finely cracked ice should be re- 
plenished at intervals. 

5. It has been found that low and non-concordant hexabro- 
mide results on pure linseed oil by the new method can nearly 
always be traced to the use of a faulty vacuum pump or to faulty 
rubber connections. Therefore, the operator should convince 
himself by test with a mercury manometer immediately before 
making the determination that his pump, as used, will give a 
vacuum of not greater than 30 mm. mercury. Heavy walled 
pressure tubing should always be used for connections. A 
faulty pump or faulty rubber connections usually means that 
the chloroform is not all evaporated from the impure hexabro- 
mide and will exert a solvent action on the hexabromide later 
on, thus giving low yields. 

6. If a Nelson rotary oil pump is available, it is an excellent 
plan to remove the last traces of chloroform by attaching the 
centrifuge tube to this type of pump for 15 minutes. The bulk 
of the solvent should be removed first by means of the water 
pump. 

7. With either pump the tube should be heated in a bath of 
60-65° C., during the evaporation of the last traces of chloro- 
form. 


230 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


BAILEY’S MODIFICATION OF STEELE AND WASHBURN METHOD 


Hexabromide Number 
References: 

The literature on the determination of hexabromide numbers 
is not very extensive. The following are the recent references 
of value: 

Chem. Tech. and Anal. of Oils, Fats & Waxes, by Lewkowitsch, 
5th Ed., Vol. I, p. 568. 

Farben Zeitung (1912) No. 3 ff. 

Muggenthaler, Inaug. Dissert. 1912, Augsburg. 

Bailey and Johnson, J. I. E. C. 10, 999. 

Principle: 

The unsaturated fatty acids when treated under proper con- 
ditions with bromine absorb at each unsaturated linkage two or 
more atoms of bromine depending on the degree of unsaturation. 
Thus at a double bond—C=C—there is obtained a saturated 
bromo product—C—C—and at a triple bond—C=C—four bro- 

Br Br 
mine atoms are absorbed to give a saturated compound 
i a 


—C—C—. The solubility in ether of the bromo derivaties de- 


ee Br 


creases rapidly with increase of bromine content. Thus the di 
and tetra bromo compounds are easily soluble, whereas the hexa 
(and octo) compounds are only very sparingly soluble. This 
fact is made use of to separate the hexa (and octo) bromo de- 
rivatives in carrying out the analytical determination. 

Status: 

The following method is applicable to the determination of 
the hexabromide number of saponifiable oils. It must be re- 
membered thatthe hexabromide number depends upon the 
method employed in making the determination. It is, there- 
fore, important that in reporting results, the particular method 
must be specified. 


Reagents and Apparatus: 
(a) Reagents: 


(1) C. P. sodium hydroxide solution of 1.4 sp. gr. 
(2) 95% alcohol. 
(3) Distilled water. 


ANALYSIS OF PAINT OILS 231 


(4) C. P. hydrochloric acid. 

(5) CO, or nitrogen. 

(6) C. P. bromine containing no non-volatile matter. 

(7) Glacial acetic acid showing no reduction with 
dichromate or permanganate in the usual test. 

(8) Wash ether. 


Shake ordinary ethyl ether with 10% of its volume of ice- 
cold distilled water. Separate the water and repeat the wash- 
ing three times. Dry the washed ether with fused calcium 
chloride over night. Decant the ether through a folder filter into 
another flask and add thin slices of sodium. Warm gently on a 
steam bath under a reflux condenser until the evolution of gas 
by action of the sodium has practically ceased and bits of freshly 
cut sodium remain bright in the ether. Distill the ether into 
a dry bottle and add an excess (at least 3 grams per liter) of 
finely powdered hexabromide of the fatty acids of linseed oil 
previously prepared. (If no hexabromide is on hand from 
previous determinations, it may be prepared as follows: In a 
centrifuge tube dissolve about five grams of the fatty acids of 
linseed oil in 25 cubic centimeters of ether. Place the tube in 
a freezing mixture and add slowly with shaking bromine solu- 
tion until a red color is permanent. Let stand for at least 
fifteen minutes and then whirl the tube in a centrifuge until 


the precipitate has settled and then pour off the ether. Rub 
up the precipitate with 20 cc. of cold absolute ether, whirl in 


a centrifuge and pour off the wash ether. Repeat the washing 
with 3 more 20 cubic centimeter portions of ether. After 
drying the hexabromide so obtained is ‘pure enough for the 
preparation of the wash ether.) Shake at intervals for two or 
three hours or allow the mixture to stand overnight. Then 
place the bottle in ice water so that the ether solution will be 
at zero or not above 2° C. for at least three hours. Decant 
the ether solution rapidly through a folded filter into a dry 
bottle and keep tighly corked in order to prevent the loss of 
ether by evaporation. 


(b) Apparatus: 


(1) Steam bath. 

(2) Gas burner. 

(3) Iron tripod, ring stand and wire gauze. 
(4) Round bottom flask of 2 liters capacity. 
(5) Separatory funnel, 500 cc. 

(6) Bell jar. 


232 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


(7) Well annealed test tubes 5” x 1”. 
(8) 50 ce. burette. 
(9) Glass stirring rods 6” x 3/16”. 
(10) Glass battery jars. 
) Graduated cylinders 10 and 50 cc. capacity for 
weighing out samples. 
(13) Centrifuge giving about 3,000 R. P. M. 
(14) A vacuum showing no higher than 40 mm. pres- 
sure. 


Determination: 

(a) Preparation of fatty acids——Weigh approximately 50 
grams of oil into a 2 liter round-bottom flask and add 40 cc. 
of NaOH solution (sp. gr. 1.4—36.50% sol.) and 40 cc. of alco- 
hol. Place the mixture on a steam bath and insert a 2-hole rub- 
ber stopper into the neck of the flask carrying a tube which 
projects into the flask so that its end is just above the liquid. 
Heat for about one-half hour, passing a stream of CO, through 
the apparatus all the while. Add one liter of hot distilled water 
and boil the soap solution to remove the alcohol, either over a 
free flame or on a steam bath. If a free flame is used about 
one-half hour’s boiling will be sufficient, but it may be neces- 
sary to insert capillary tubes to prevent bumping of the liquid. 
If the solution is heated on the steam bath, usually 2 to 3 hours 
are required. After removing the alcohol, the solution is cooled 
somewhat and then acidified with dilute HCl (1:1). Warm the 
mixture until the fatty acids form a clear layer, continuing to 
pass CO, through the system all the time. The fatty acids are 
separated from the aqueous layer by means of a 500 cc. Sep- 
aratory funnel. The funnel is filled with the mixture, and the 
fatty acids will float on top, and the aqueous portion is run off. 
The remainder of the mixture in the flask is added to the fun- 
nel and the aqueous portion again run off. A brisk stream of 
CO, is passed into the funnel to replace the air. 300 cc. of 
hot distilled water is added and the mixture is vigorously 
shaken. After the fatty acids collect on top the aqueous por- 
tion is run off. This washing is repeated until the water is 
neutral to methyl orange, three washings usually being suffi- 
cient. The warm fatty acids are run into a centrifuge tube 
(1” x 5”) and whirled for about one minute to collect any re- 
maining water at the bottom. They are then filtered by de- 
cantation on to a folded filter under an evacuated bell jar and 
kept in a well-stoppered bottle. 


ANALYSIS OF PAINT OILS 233 


(0) Preparation of the hexabromides—wWeigh accurately in 
a weighed contrifuge tube (1” diam. x 5” long) as nearly as 
possible one gram of fatty acids. It was found that in the case 
of linseed oil better results are obtained by keeping the weight 
of the sample as near to one gram as possible, so the deviations 
from this should not be more than plus or minus 0.02 gram. 
Dissolve the fatty acids in 25 cc. of the specially prepared ether 
and place the tube in a freezing mixture kept at about —5° C. 
made by adding a little HCl to finely cracked ice. Add bromine 
solution* from a burette at the rate of about one or two drops 
per second, shaking the tube well during the addition until a 
deep red color is produced. This should not be done in direct 
sunlight. The tube is then allowed to stand in an ice chest over- 
night (about 14 hrs.), the proper precautions being taken to 
prevent the loss of solvent by evaporation by inserting a stopper. 

It is necessary to let the tube stand for this period of time be- 
cause in the case of oils which contain only a small amount of 
linolenic acid (soya bean oil is a good example) the precipita- 
tion of the hexabromide proceeds more slowly than in the case 
of an oil with a larger content of linolenic acid (linseed for 
example). 

Next morning cool the tube by immersion in a bath of cracked 
ice and rub up the precipitate by means of a weighed glass rod, 
being sure to loosen any material adhering to the side of the 
tube. Whirl the tube in a centrifuge till the precipitate forms 
a hard cake on the bottom, cool in the ice bath, and decant the 
ether. Add 20 cc. of the wash ether previously prepared and 
cooled to 0° C. and rub up the precipitate with the glass rod. Re- 
turn the tube to the ice bath and when cold whirl it in the 
centrifuge. Return the tube to the ice bath and then remove 
the ether by decantation. Repeat this washing twice more. 
After the last washing incline the tube and carefully tap it to 
spread the hexabromide precipitate part of the way up the 
sides. Warm the tube in water at 60° C. until most of the ether 
has evaporated, then attach it for 15 minutes to a vacuum line 
showing a pressure of 30-40 mm. keeping the temperature 
around 60° C. Wipe the tube dry and allow it to stand in the 
balance at least 15 minutes before weighing. To the weight of 
the precipitate in the tube add the weight of the slight amount 
adhering to the glass rod. This total weight of precipitate mul- 


*5 ec. bromine, 25 cc. glacial acetic acid made up just before use. 


234 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


tiplied by 100 and divided by the weight of fatty acids taken, 
gives the hexabromide percentage. 

Notes: (1) The fatty acids are used instead of the glyceryl 
esters because the latter give inconcordant results. 

(2) In the case of linseed oil, the weight of the sample should 
be kept as near one gram as possible. 

(3) Care should be exercised in preparing the wash ether for 
if it is unsaturated with hexabromides according to directions, 
the results will be low. 


CO-OPERATIVE WORK ON HEXABROMIDE METHODS AS CONDUCTED 
BY SUB-COMMITTEE III OF COMMITTEE D-1, A. S. T. M. 


Comments made by the various observers are abstracted here- 
with: 

S. and P. Waldstein state that when a large percent- 
age of soya bean oil is present in an oil there is formed 
a large percentage of tetrabromide which may not be 
completely washed out. They recommend in such in- 
stances to increase the portions of ether to 25 or 30 cc. 
or to increase the number of washings to 5 or 6 in order 
to overcome high results. 

The chairman of the sub-comneeaee has done some 
experimental work with the idea of developing a method 
of determining the hexabromide value of oils volu- 
metrically. It was found that the bromine absorption 
number of the fatty acids of linseed oil were higher 
than for soya bean oil in some preliminary volumetric 
work. It is known that the bromine substitution num- 


TABLE XL.—The Results of Various Observers Working on the Two Methods 
Are Given in the Table Below—Hexabromide Values 


Steele-Washburn Method Bailey 
hikes Modifica- 
tion of 
Steele- 
Oil z Washburn 
ils I Ze acl € 5 : Method 
58) 2| 2/28 Blas) g)8)5| 2) Bleg 
a.0| 2 a | 20! 3 Fed Sa AS M1 a{/aiss 
On| am | O | E |e Olmi-a 
100 per cent Pure Raw Linseed Oil. . .|45.9/46.4/46 .6/45.4/46.0 46.2146, 6/45.4/46.1/40.5/42.7/41.6 
85 per cent Pure Raw Linseed Oil... 
39.3)... ./41.8/39.1/41.9/39.8/41.9/39_ 1/40, 4/34.9137.5136.2 
15 per cent Soya Bean Oil......... : 
75 per cent Pure Raw Linseed Oil. . 
36 .4|/38.4/38. 2/36 .0/37.2/36. 1/38 .4/36.0137.0/31.5134.5/133.0 
25 per cent Soya Bean Oil......... 
65 per cent Pure Raw Linseed Oil. . 


! 
30. 8/33 .4/34.8/30.5)/33.8/33.5/34.8/30.5/32.8/26.7/31.4|29.6 


_35 per cent Soya Bean Oil; .* 3.2%.. 


ANALYSIS OF PAINT OILS 


235 


ber of linseed oil fatty acids is low while the fatty 
acids of soya bean oil have a low addition number. 
Considerable further work, however, will be necessary 


in order to develop a method that will be satisfactory. 


TABLE XLI—Jodine and hexabromide numbers of raw and treated 
linseed oil 


B 


PRE WOINDHRON NON 


OL Iodine H : 
exabromide No. 
No. Substance ee Siacla. Method 
anus 
By A By 
553 | Linseed oil from North American seed..... 176.2 a 
Boo : Pay ‘ . Se Seas, cole pegs we FR : 
553 _ . : " - ine A AME: Ng ad SC ee 46.3 
553 : ae : : ee Go 46.5 
a een ee bees 46.3 
553 “ oe ae + = eran Nairgl2 a Mamie Ata 43.6 
553 xe pera 3 s ue Se Suey ight Regs pans a 39.2 
oe : i Con : gE aan ce 39.1 
565 | Linseed oil, commercial refined............ Le # fs < 
563 «“ 4 Petite tan SE a, Bo 
é s “ Ch od ah RN ee a Re es 43.8 
a : i . UES 6a rag ana ser ec aes St Aa 40.5 
574 | Linseed oil (Bu. Hieoide. sample). 26: sasses 183.0 nae 
574 a Ra ge ee We No iad ace 
Ga St Pt ieee ed iG a 0. CARED LM co? A7.1 
Meee o 
) oN ia tant, Raa oe Ie Rig Pees ASR Sep OE eR 46.2 
Me 45.7 
535 | Lins’d oil Ext’d from Argentine seed....... 189.8 50.0 49 
535 = c - ‘ is Cae mates fy NE Dna ie MB (pean MuckoO 
535 L es : : Ie aot al tater ig Seetiame nae A eS 50 
641 | OL 553 + 5% (1) tung oil Grier sass 6 22. LG GAS il ae bere a 
641 are st us : eR ere eter A eed a mT hate Sh 
rig TDS ey ee Sete er A LG LE Sit ee ae 44 
ee “4 
643 ee eet 20) Reis) Set eet eh Ca a 1D2c5 we ee: 41 
643 erat = Wel aE A ED RR os ARO be 42 
644 eerie eo erinding japan. 2......... 164806 es 39 
644 pee s s IS Ne eo, SAR RGR Ne h Rrde yar A caRy Tai 39 
CN 0 . Bia athe ek cae: AGS OC See ee 42 
a ee 41 
646 Oo i Beebe 2 ESR! eR To 7a ah eee 40 
646 | « « : a bE OP aa aN ae Meat Nima aCe acre ee das 39 
588 « « 4+ 10% (1) linoleate drier de RUBE 165.6 ae 
588 ~ me i APOE NE PR ter he S. epn ea ree: ; 
589 Cet 20%," (1) “ aig! A epee 169.3 45.3 
589 ag: 2 NRE A ris ot We ater eee Bee ty AQT 
589 aS e * So a Pg OR Saad See 43.6 
583 “« « + 0.2% manganese drier* ROR RL: oh 168.6 Bee 
583 ak we: . a yd M ames diated Sales ae eons 
ay : 2 + 0.057% a ; he ee 171.0 a 
561 | Linseed oil, commercial...........-..-+-- 173.8 41.8 
561 = TLE Fake AR ee aan GS Src a amas ete 
359 M «heavy bOCIGd “+ Si ou sabes G iee ak 80.8 11.8 


(1) Added without treating oil. 


(*) Manganese linoleate boiled in at 250° C. 


236 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Conclusions.—The Steele-Washburn method of determining 
hexabromides has given closely concordant results in the hands 
of several different operators, and is apparently well adapted 
for determining the purity of raw linseed oil. It is recom- 
mended that further work be carried on with the object of 


shortening the method. 


HENRY A. GARDNER, 
Chairman. 


Through the kindness of Mr. Herbert S. Bailey and Mr. 
Baldsiefen of the -Experimental Station, E. I. du Pont de 
Nemours & Co., there are presented herewith two tables (LI 
and LII) showing the iodine and hexabromide numbers of 
raw and treated linseed oils, and of soya bean oil, tung oil, and 
various mixtures thereof. It is believed that the data presented 
in these tables will be of great service to the paint chemist who 
intends to carry on hexabromide work. 


TABLE XLII—Iodine and hexabroimide numbers of soya bean, tung and lin- 
seed-soya bean mixtures 


Ow os 
Zo = 
i os 
Hep sam 
S ei ele 
A 3 Ooo OF 
vs b 8 eae a 
No. Substance ies Re ea 
~ a co 
By A. | By B. | By B. 
310 Soya bean os raw 5.) eee eee 123.2 a 6.5 4.2 
310 . OUR SS a a 0 a 6; 1 See 4.9 
310 4 Fe hee ee ek at aes De 6.3) 5 ee 3.6 
565 Soya bean oil, raw commercial. .... 133.2 1.6 
565 . eS * BS ee 5.0 
658 i “©” eold pressed. = 3.02.51 4.2 ee 8.41 Peer 
658 . rape te pi Oem newer 9.388 | 7.54 
659 Soya bean oil, cold. pressed... ... .:.W.o5 joe 5.95 5.35 
659 , oo sues Ree OT Og wae aels She al oe 5.76 5.65 
670. | Soya bean oil, extracted, 0). .:.2.. 21, Ve 3.9 
622 Tung oil. ee ae is ee 2 0.0 0.0 
572 £0% OL 563: 50% OL 310. 954 oe 26.0 23.0 
572 Re cata meee ey 23.6 
572 50% OL.553 + 50% OL 670. 0.1. a 24.3 23.3 
572 Fi ane Be eS er 24.6 24.3 


CHAPTER XXVI. 


EXAMINATION OF FLAXSEED* 


Sample is quartered until 500 grams are obtained. In quar- 
tering, seed must be poured at center of pile to evenly distribute 
seed and impurities. All of the dirt which settles to the bottom 
must be carefully brushed up and added to the pile. Screen the 
500 gram sample through 10 mesh until about 50 grams remains 
on the screen. The residue is hand picked and everything other 
than linseed is set aside and weighed with the dust. The 
clean seed obtained at this picking is added to what has passed 
through the 10 mesh screen. The seed is then passed through a 
20-mesh screen, rubbing the seed around in the screen so as to 
remove any seed attached to it. The under size is collected and 
weighed after the coarse pickings have been added to it. This 
constitutes the first dust. The partially cleaned linseed is then 
reduced to 50 grams in a rifflesampler. This is divided into two 
25-gram portions which are hand picked separately and the 1m- 
purities weighed separately. All linseed portion, whether dried 
seed or broken seed, is to be put with the linseed. After cor- 
rected calculation, the total impurities are obtained. The im- 
purities found in the second picking should agree within 60 
milligrams. 7 

Oil in Flaxseed.—A 3-gram sample of the clean seed is 
weighed out and is ground in an agate mortar with an equal part 
of fine sea-sand which has been washed with hydrochloric acid. 
The ground sample is placed in a Soxlet thimble and extracted 
with redistilled ether for three hours. The distillate is placed 
in a weighing dish and the ether is removed by evaporation. 
The residue is then dried for one-half hour at 103° C., and the 
oil is weighed. | 

Oil in Oil Cake—A 10-gram sample of undried oil cake is 
placed in a Soxlet thimble and extracted in the same way as 
described under Oil in Flaxseed. 

Water in Oil Cake-—Weigh 5 grams of oil cake and place in 
flask fitted with clean cork. Weigh flask, cork and contents; 
connect with hydrogen generator, and start flow of hydrogen 
at the rate of 2 bubbles per second. Place flask in paraffin bath 


*Contributed by R. L. Hallett. 
237 


238 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


at a temperature of 110° C., and heat in current of hydrogen 
for two hours. Disconnect tubing, and wipe clean of paraffin 
while hot, with absorbent paper. Cool and draw dry air through 
flask to remove hydrogen. Disconnect, replace original cork, 
and weigh. Loss of weight reported as moisture. 

Protein in Oil Cake.—Protein is found by determining total 
nitrogen by the Kjeldahl method, calculating it to protein. 


: 
; 
a 
7 
3 
’ 


CHAPTER XXVII. 


TENTATIVE SPECIFICATIONS FOR RAW TUNG OIL AND 
METHODS OF TEST A. §. T. M. 


Raw tung oil shall conform to the following requirements: 


Maximum. Minimum. 


CCHICEeTavivy ab LD2De Cong eden 0.943 0.940 
15.5° 

Acid number (Alcohol-Benzol)...........-- aD cat ees ee 

BOT ALON TUMDECL ioc ccnepectec 195 190 

Unsaponifiable matter, per cent..................... DES cake fee ees 

Pret VAC tIVGnINGES Ate ZO) Conc eee mttaer 1.520 1.5165 

Pere DST OW LYS) ae siltstone 163 
Belieatine testy MiINUles ee ea, eA ‘ 


METHODS OF TESTING 


Solutions Required.—The following reagents will be required: 

Standard Sodium Thiosulfate Solution.—Dissolve pure sod- 
ium thiosulfate in distilled water that has been well boiled to 
free it from carbon dioxide in the proportion so that 24.83 g. 
erystallized sodium thiosulfate will be present in 1000 cc. of the 
solution. It is best to let this solution stand for about two weeks 
before standardizing. Standardize with pure resublimed 
iodin. (See Treadwell-Hall, Analytical Chemistry, Vol. II, third 
edition, p. 646.) This solution will be approximately N/10 
and it is best to leave it as it is after determining its exact iodine 
value, rather than to attempt to adjust it to exacly N/10 
strength. Preserve in a stock bottle with a guard tube filled 
with soda lime. 

Starch Solution.—Stir up 2 to 3 g. of potato starch or 5 g. 
soluble starch with 100 cc. of 1-per-cent salicylic acid solution, 
add 300 to 400 cc. boiling water, and boil the mixture until the 
starch is practically dissolved. Dilute to 1 liter. 

Potassium Iodide Solution—Dissolve 150 g. of potassium 
iodide free from iodate in distilled water and dilute to 1000 ce. 

lodine-Monochloride Solution Dissolve iodine in glacial 
acetic acid that has a melting point of 14.7 to 15° C. and is free 
from reducing impurities in the proportion so that 13 g. of 
iodine will be present in 1000 cc. of the solution. The prepara- 
tion of the iodine-monochloride solution presents no great diffi- 
culty, but it shall be done with care and accuracy in order to 
obtain satisfactory results. There shall be in the solution no 


239 


240 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


5 cc. Sample-=.\.. 


Cottonseedor : | ; QE 
Soya Brie ae red 
Vertical Section. 
— OPECIFICATIONS — 
A. Beaker Glass 800 cc. 


D. Test Tubes; lScm, x 16mm. 


B. Cover Plate (/ron or Wood.) E. Thermometer,- Small Range. 


C. Collar Support ( Rubber 
Stopper No. 6.) 


FIGURE 98 

Tung Oil Heat Test Apparatus (Revised 1920) 
Note.—Collars C may be omitted and tubes supported in present place 
by oa wire gauze placed in bottom of oil bath and resting on bottom 
of beaker. 


F. Glass Rods, (3mm. with 
Cork Stoppers ) 


SPECIFICATIONS FOR TUNG OIL 241 


sensible excess either of iodine or more particularly of chlorine, 
over that required to form the monochloride. This condition 
is most satisfactorily attained by dissolving in the whole of the 
acetic acid to be used the requisite quantity of iodine, using a 
gentle heat to assist the solution, if it is found necessary. Set 
aside a small portion of this solution, while pure, and pass dry 
chlorine into the remainder until the halogen content of the 
whole solution is doubled. Ordinarily it will be found that by 
passing the chlorine into the main part of the solution until the 
characteristic color of free iodine has just been discharged, 
there will be a slight excess of chlorine, which is corrected by 
the addition of the requisite amount of the unchlorinated portion 
until all free chlorine has been destroyed. A slight excess of 
iodine does little or no harm, but excess of chlorine must be 
avoided. 

Chloroform.—Should be U. S. P. 

Standard Sodium Hydroxide Solution—Prepare a stock con- 
centrated solution of sodium hydroxide by dissolving NaOH in 
water in the proportion of 200 g. NaOH to 200 cc. water. Allow 
this solution to cool and settle in a stoppered bottle for several 
days. Decant the clear liquid from the precipitate of sodium 
carbonate into another clean bottle. Add clear barium hydrox- 
ide solution until no further precipitate forms. Again allow 
to settle until clear. Draw off about 175 cc. and dilute to 10 
liters with freshly boiled distilled water. Preserve in a stock 
bottle provided with a large guard tube filled with soda lime. 
Determine the exact strength by titrating against pure benzoic 
acid (C,H.COOH) using phenolphthalein as indicator. (See 
Bureau of Standards Scientific Paper No. 183.) This solution 
will be approximately N/4, but do not attempt to adjust it to 
any exact value. Determine its exact strength and make proper 
corrections in using it. 

Alcoholic Sodium Hydroxide Solution.—Dissolve pure NaOH 
in 95-per-cent ethyl alcohol in the proportion of about 22 g. per 
1000 cc. Let stand in a stoppered bottle. Decant the clear 
liquid into another bottle, and keep well stoppered. This solu- 
tion should be colorless or only slightly yellow when used; it 
will keep colorless longer if the alcohol is previously treated 
with NaOH, (about 80 g. to 1000 cc.), kept at about 50° C. for 
15 days, and then distilled. For an alternate method see Jour- 
nal, American Chemical Society, 1906, p. 395. 


242 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Half Normal Sulfuric Acid Solution.—Add about 15 cc. H,SO, 
(sp. gr. 1.84) to distilled water, cool and dilute to 1000 cc. De- 
termine the exact strength by titrating against freshly standard- 
ized NaOH or by any other accurate method. Either adjust to 
exactly N/2 strength or leave as originally made, applying ap- 
propriate correction. 

Methods.—The oil shall be tested in accordance with the fol- 
lowing methods: 

General.—The laboratory sample shall be thoroughly mixed 
by shaking, stirring, or pouring from one vessel to another and 
the samples for the individual tests taken from this thoroughly 
mixed sample. 

Specific Gravity.—Use a pyknometer accurately standardized 
and having a capacity of at least 25 cc., or any other equally 
accurate method, making the test at 15.5° C., water being 1 at 
1D... 2G. 

Acid Number.—Weigh from 5 to 10 g. of the oil. Transfer 
to a 300-cc. Erlenmeyer flask. Add 50 cc. of a mixture of 
equal parts by volume of 95-per-cent ethyl alcohol and ce. p. re- 
agent benzol. (This mixture should be previously titrated to a 
very faint pink with dilute alkali solution, using phenolph- 
thalein as an indicator.) Add phenolphthalein indicator and 
titrate at once to a faint permanent pink color with the stand- 
ard sodium hydroxide solution. Calculate the acid number 
(milligrams KOH per gram of oil). 

Saponification Number.—Weigh about 2 g. of the oil in a 
300-cc. Erlenmeyer flask. Add 25 cc. alcoholic sodium hydroxide 
solution. Put a condenser loop inside the neck of the flask and 
heat on the steam bath for one hour. Cool, add phenolphthalein 
as indicator, and titrate with N/2 H,SO,. Run two blanks with 
the alcoholic sodium hydroxide solution. These should check 
within 0.1 cc. N/2 H,SO, From the difference between the 
number of cubic centimeters of N/2 H,SO, required for the 
blank and for the determination, calculate the saponification 
number (milligrams KOH required for 1 g. of the oil). 

Unsaponifiable Matter—Weigh 8 to 10 g. of the oil. Trans- 
fer to a 250-cc. long-neck flask. Add 5 cc. of strong solution of 
sodium hydroxide (equal wieghts of NaOH and H,O), and 50 cc. 
95-per-cent ethyl alcohol. Put a condenser loop inside the neck 
of the flask and boil for two hours. Occasionally agitate the 
flask to break up the liquid but do not project the liquid onto the 


SPECIFICATIONS FOR TUNG OIL 243 


sides of the flask. At the end of two hours remove the con- 
denser and allow the liquid to boil down to about 25 cc. 

Transfer to a 500-cc. glass-stoppered separatory funnel, rins- 
ing with water. Dilute with water to 250 cc., add 100 cc. redis- 
tilled ether. Stopper and shake for one minute. Let stand until 
the two layers separate sharp and clear. Draw all but one or 
two drops of the aqueous layer into a second 500-cc. separatory 
funnel and repeat the process, using 60 cc. of ether. After thor- 
ough separation draw off the aqueous solution into a 400-cc. 
beaker, then the ether solution into the first separatory funnel, 
rinsing down with a little water. Return the aqueous solution 
to the second separatory funnel and shake out again with 60 
ec. of ether in a similar manner, finally drawing the aqueous 
solution into the beaker and rinsing the ether into the first 
separatory funnel. 

Shake the combined ether solution with the accumulated water 
rinsings and let the layers separate sharp and clear. Draw off 
the water and add it to the main aqueous solution. Shake the 
ether solution with two portions of water (about 25 cc. each). 
Add these to the main water solution. 

Swirl the separatory funnel so as to bring the last drops of 
water down to the stopcock, and draw off until the ether solu- 
tion just fills the bore of the stopcock. Wipe out the stem of 
the separatory funnel with a bit of cotton on a wire. Draw 
the ether solution (portionwise if necessary) into a 250-cc. flask 
and distill off. While still hot, drain the flask into a small 
weighed beaker, rinsing with a little ether. Evaporate this 
ether, cool and weigh. 

Refractive Index.—Use a properly standardized Abbé refrac- 
tometer at 25° C., or any other equally accurate instrument. 

Iodine Number.—Place a small quantity of the sample in a 
small weighing burette or beaker. Weigh accurately. Transfer 
by dropping from 0.16 to 0.19. g. to a 500-cc. bottle having a 
well-ground glass stopper, or an Erlenmeyer flask having a spe- 
cially flanged neck for the iodine tests. Reweigh the burette or 
beaker and determine the amount of sample used. Add 10 ce. 
of chloroform. Whirl the bottle to dissolve the sample. Add 
10 ec. of chloroform to each of two empty bottles like that 
used for the sample. Add to each bottle 25 cc. of the Wijs solu- 


NotTE.—The unsaponifiable oil from adulterated drying oils is volatile and 
will evaporate on long heating. Therefore heat the beaker on a warm 
plate, occasionally blowing out with a current of dry air. Discontinue 
heating as soon as the odor of ether is gone. 


244 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


tion and let stand with occasional shaking for 30 minutes in a 
dark place at a temperature of from 21 to 23° C. Add 10 ce. 
of the 15-per-cent postassium iodide solution and 100 cc. of 
water, and titrate with standard sodium thiosulfate using starch 
as the indicator. The titrations on the two blank tests should 
agree within 0.1 cc. From the difference between the average 
of the blank titration and the titration on the samples and the 
iodine value of the thiosulfate solution, calculate the iodine 
number of the samples tested. (Iodine number is given in centi- 
grams of iodine to 1 g. of sample.) * 

Heating Test.—Test tubes containing the oil should be 15 cm. 
by 16 mm., with a mark near the bottom to indicate 5 cc., and 
closed by a cork so perforated that a glass rod 3 mm. in diameter 
can move freely. 

Fill an 800-ce. glass beaker (height, 13 cm.; diameter, 10 
em.) with cottonseed oil or soya bean oil to a height of 7.5 cm. 
Place a thermometer so as to be 1.5 cm. from the bottom of the 
bath. 

Use a nitrogen-filled, chemical thermometer; engraved stem; 
total length 4 to 414 in., graduated from 210 to 310° C. in 2° 
intervals; the length between 210 and 310° C. not less than 
214 in. Thermometer glass shall be well annealed. 

When the bath temperature is 293° C. (560° F.) and very 
slowly rising at this point, place the tube containing 5 cc. of 
the oil to be tested and the tube containing 5 cc. of a control 
sample of known value, so that the bottom of each tube is level 
with the lowest part of the bulb of the thermometer. If desired, 
the collars C may be omitted and the tubes allowed to rest upon 
a piece of wire gauze placed in the bottom of the oil bath so 
that the tubes will be 1.5 cm. from the bottom of the bath. Note 
the time. Remove the source of heat for about 45 seconds and 
then reapply. Before 2 minutes have elapsed the temperature 
of the bath will have fallen to 282° C. (530° F.), at which point 
it should be kept as steady as possible. When the samples have 
been in the bath 9 minutes, raise the glass rods at intervals of 
14, minute. Note the time when each sample becomes firmly set. 
At this period the oil will be so stiff that the entire tube may he 
lifted by aid of the rod if the collar C is omitted from the ap- 
paratus. As setting or jellying takes place within a few seconds 
of fluidity, a good end determination is afforded. Remove the 


* It is always well to include a test on a sample of tung oil of known 
iodine value. This may be kept in a dark-colored bottle as a standard. 


ee a ee ee ey 


SPECIFICATIONS FOR TUNG OIL 245 


specimens. Heat the bath again to 293° C., and repeat the ex- 
periment with fresh portions of the sample. 

No stirrer is used in the bath. A screen around the bath en- 
ables the temperature to be more easily reached. When the 
bath oil has become tarry and viscid, it should be renewed; 
otherwise heating may be irregular. 

Quality Test.*—Into an ordinary agateware casserole, having a 
bottom diameter of 3 in., weigh 150 g. of the tung oil to be tested, 
and set the casserole on a wide-flanged tripod having a 3-in. open- 
ing. The object of the flange is to prevent super-heating of the 
sides of the casserole. Heat rapidly with a full Bunsen flame, 
stirring with a thermometer, until the heat reaches 540° F. 
(282.2° C.) Turn down the flame and hold the heat as near 540° 
F., (282.2° C.) as possible stirring with the thermometer, until on 
lifting the latter the oil drops with a pronounced string, showing 
that polymerization has started. The time required after reach- 
ing 540° F. (282.2° C.) until the string is noted, is the time of 
the heat test. For pure tung oils this will not exceed eight min- 
utes. As soon as the oil strings, remove the lamp and the ther- 
mometer, and stir with a stiff spatula until the oil is solid. After 
stringing, a pure tung oil will require not over 40 seconds more 
to become solid. When solid, allow to stand just one minute, then 
turn out, upside down, on clean paper and cut with a clean 
spatula. Pure tung oil gives, a gel that is dry, not adhering to 
the spatula when cut, that is firm, crumbling under pressure of 
the spatula without sticking, and the cut portions should crumble 
under pressure like dry bread crumbs. Adulterated tung oil 
gives a gel that is soft, sticky, and which will not crumble. 


It has been found that the optical dispersion of tung oil is ex- 
tremely high as compared to that of many other oils. Based on 
this, Holley has worked out a method to determine the purity of 
tung oil (Holley, Analysis of Paint Vehicles, 1920, p. 81). This 
method, however, is not commonly in use because of the expense 
and difficulty of obtaining the type of apparatus used for the pur- 
pose. It is believed, nevertheless, that optical dispersion methods 
are of great value for the examination of tung oil and that they 
should be used when the apparatus and instruments are avail- 
able, as additional or confirmatory tests. As a rule, determina- 
tion of specific gravity, refractive index, and quality tests, as 
outlined above, afford sufficient information to judge the purity 
and value of tung oil. 


* Furnished by R. S. Worstall. 


CHAPTER XXVIII. 


ANALYSIS OF VARNISH 


The testing of oleo-resinous varnish should largely be of a 
physical nature. Such properties as odor, consistency, clarity, 
flowing, time of drying, character of finish, hardness, resistance 
to moisture and abrasion, elasticity, etc., point out the real value 
of a varnish. Chemical tests that give additional information, 
sometimes of a valuable nature, are as follows: Flash point, acid 
number, ash, character of solvent, fixed oil and resins. 

Flash Point.—A nickel or iron crucible of 60 mm. diameter 
and 40 mm. height is filled with the varnish to within 20 mm. 
of the top. It is then supported in a water bath in such a man- 
ner as to be about two-thirds immersed in the water. The water 
should, be from 15° to 20° C. at the start and should be heated 
slowly so that the temperature of the varnish as indicated by 
a thermometer suspended in it, will show a rise of about 1 de- 
gree per minute. Test for flash at each half degree, using a 
very small flame. (See also A. S. T. M. use of Tag closed tester. ) 

Acid Number.—Ten to 20 grams of the varnish are weighed 
into a small Elenmeyer flask, 50 ce. neutral alcohol added, and 
a small funnel inserted in the neck. Heat on the water bath for 
one-half hour, with occasional shaking. Allow to cool some- 
what, add two drops of phenolphthalein indicator and titrate 
with tenth-normal potassium hydroxide solution. The acid 
number is the number of milligrams of KOH required to 
neutralize each gram of the varnish. Use of a mixture of equal 
volumes of alcohol and benzol 90° gives the true acid number 
of a varnish including colloidal acidity that would not be indi- 
cated by alcohol alone. 

Ash.—Weigh in a porcelain or fused silica crucible several 
grams of the varnish. Burn off over a small Bunsen flame, 
using great caution to avoid boiling over and spattering. When 
all combustible matter is destroyed, weigh the ash and if desired 
analyze it. 

Solvent—Steam distillation of a portion of the varnish will 


remove the solvents, leaving a residue of fixed oils and varnish _ 


resins, which may be weighed after driving off the water. The 
distillate should be examined as recommended under Turpentine 


246 


ANALYSIS OF VARNISH 247 


FIGURE 99 


Apparatus for determining gas re- 
sistance of varnish. See Interdepart- 
mental Specifications, back of volume. 


FIGURE 100 


Apparatus for determining draft resistance of varnish. See Inter- 
departmental Specifications, back of volume. 


248 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Specifications. The amount of mineral spirits and turpentine 
may thus be determined. 

It is customary to conduct the steam distillation upon 50 
grams of varnish in a 500-cc. Erlenmeyer flask placed in an oil 
bath maintained at about 130° F. The distillate may be col- 
lected in a separatory funnel. The water may then be drawn 
off and the distillate examined. 

A much more rapid and fully as accurate a method for de- 
termining the percentage of volatile is as follows. This method, 
however, does not yield the actual volatile for subsequent ex- 
amination. 

Percentage of Volatile-—Place a portion of the sample in a 
stoppered bottle. Weigh the container and sample. Transfer 
about 1.5 grams of the sample to a flat bottom metal dish about 
8 cm. in diameter (a friction top can plug). Weigh the bottle 
again and by difference calculate the exact weight of the portion 
of the sample transferred to the metal dish. Heat the dish and 
contents in an oven maintained at 105° to 110° C. for 3 hours. 
Cool and weigh. From the weight of the residue left in the 
dish and the weight of the sample taken, calculate the percent- 
age of non-volatile residue. 

Fixed Oils and Resins.—In the above determination, the total 
amount of fixed oils and resins is obtained. It is a difficult 
matter, however, to determine the exact percentage and char- 
acter of resins that. have been used in the manufacture of the 
varnish. This is due to the fact that during the process of 
heating oils in the presence of resins many intricate chemical 
changes are brought about, a considerable portion of the resins 
being distilled off in the form of vapors and combinations of 
the oil brought about that are difficult of separation. One of 
the best methods, however, of separating the fixed oils and 
varnish resins is carried out in the following manner: 

A portion of about a half ounce of the varnish resin should be 
placed in a 3800-cc. tared beaker. There should then be added 
about 200 cc. of ice-cold petroleum ether. After stirring the 
beaker should be covered and allowed to stand, preferably in a 
dish containing ice. In an hour’s time the resinous ingredients 
will be found precipitated at the bottom of the beaker or adher- 
ing to the side thereof (with the exception of rosin, which is 
largely soluble in petroleum ether). The precipitated resins 
should be washed with fresh portions of cold petroleum ether 


ah tend Nt |i i ba 


ANALYSIS OF VARNISH 249 


two or three times, pouring the decanted portions into a large 
bottle. The combined portions of petroleum ether may then be 
filtered through a tared filter, adding by the aid of a stirring 
rod the resins contained in the beaker. The filter paper and the 
beaker with the resins may then be dried at 100° C. and weighed. 
The combined filtrates may be distilled to obtain the fixed oil as 
a residue, which may be examined for constants. (This fixed 
oil may contain rosin.) The amount of rosin contained in a 
varnish may be roughly ascertained by thoroughly shaking in a 
separatory funnel a portion of the varnish with a large quantity 
of absolute alcohol. The rosin may be obtained by evaporation 
of the alcoholic extracts. The fixed oils after oxidation or poly- 
merization, as caused by the heating of the varnish during 
manufacture, are not readily soluble in alcohol. 

Separation of Polymerized Oils and Resins.—In the making 
of varnish, most oils become oxidized or polymerized to a condi- 
tion resembling resins. For instance, when a varnish is ex- 
amined for resins by the above method, it will often be found 
that a considerable amount of matter insoluble in petroleum 
ether will be obtained even when hard resins are absent. The 
insoluble substance is oxidized or polymerized oil. It may be 
differentiated from varnish resins by the fact that it may be 
saponified by alcoholic potash. 

This method, as used by the regulatory division of the State 
of North Dakota, is the original method published by E. W. 
Boughton of the Bureau of Standards (see U. 8S. Bureau of 
Standards Technologic Bulletin 65), as modified in North Da- 
kota. Although it involves a tremendous amount of work, it is 
probably the most accurate method for the separation of polym- 
erized oils and resins. The method follows Boughton’s original 
scheme very closely. The use, however, of ice-cold ether and ice- 
cold water is probably an advantage in that the ether separa- 
tions are quicker and sharper. In Boughton’s original method, 
the material extracted by ether from the first saponification 
mixture of acids and fatty acid soaps is termed unsaponifiable 
matter. In the North Dakota revision, the proposal is made to 
add this same ether extract to the resin portion. This consti- 
tutes a somewhat radical difference between the two schemes 
and clearly brings out the fact that neither Boughton’s method 
nor the North Dakota method can be relied upon to give the 
true oil content of present-day varnishes. For instance, at 


250 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


least one of the varnishes on the market today contains wool 
fat (degras). In Boughton’s method this product would show 
up as unsaponifiable matter, while in the North Dakota method 
the unsaponifiable part of the wool fat would be included in the 
resins. This same difference would be true of a varnish con- 
taining paraffin. On the other hand, a varnish made of tung oil 
and cumarin resin would show a high unsaponifiable and resin 
content by Boughton’s method, while the North Dakota method 
would indicate the cumarin as resin. 

In view of the above, it is quite apparent that neither one of 
these methods should be included as a part of any routine 
method of analysis of a varnish but should be merely classed as 
“stunt” tests for a research laboratory, where an insight into 
the ingredients of a varnish is desired. All of which brings 
out the absolute futility of a varnish analysis as a basis of 
evaluation. Physical tests afford the only reliable data in judg- 
ing the properties of an oleo-resinous varnish. 

Method.—Weigh by difference from 4 to 6 grams of the 
varnish into a 125-cc. Erlenmeyer flask, add 25 ec. of water and 
boil gently until not over 5 cc. of water is left. This is best 
performed by placing the flask in an oil bath, and by passing a 
stream of carbon dioxide through the mixture during the evap- 
oration. Then add 25 cc. each of half normal alcoholic potash 
and benzol, and reflux for one hour. 

Evaporate the solution down to about 10 ce. and transfer to a 
500-cce. globe-shaped separatory funnel, rinsing the flask well 
with water, alcohol and ether. Add 100 cc. each of water and 
ethyl ether and shake well, using a moderate circular motion. 
In this and all similar operations use ice-cold ether and ice- 
cold water. The shaking should be repeated three times. Should 
an emulsion form and not break within five minutes, add 2 ec. 
of alcohol. 

Draw off the aqueous layer into another separatory funnel 
and wash the ether layer twice with cold water. Add the wash- 
ings to the aqueous layer and transfer the ether layer to a 
weighed Erlenmeyer flask labeled “Gums.” Acidify the aqueous 
layer and completely extract with ether. Transfer the ether 
solution to the Erlenmeyer flask into which the varnish was 
weighed and distill off the solvent, using a vertical condenser. 
Then add 10 cc. absolute alcohol and evaporate on a steam bath. 
This is to remove the water present. Distill off the solvent in 


: 
) 
; 
4 
| 
: 
; 
; 
; 
F 


a ee ee a gare OT We 


ANALYSIS OF VARNISH 251 


the “Gums” flask whenever the flask becomes half-full. All 
ether solutions of unsaponifiable matters and the resins acids 
that are separated out from subsequent extractions are trans- 
ferred to this flask. 

To the residue extracted from the acid solution add 20 cc. of 
absolute alcohol and 20 cc. of a mixture of 4 parts of absolute 
alcohol and 1 part of concentrated sulphuric acid. Reflux for 
five minutes, transfer to a separatory funnel, rinsing the flask 
with water and ether, and add 100 cc. of ether. Shake well, 
add 100 ce. of a 10-per-cent solution of sodium chloride, and 
shake several times. Draw off the aqueous layer and extract 
with 50 cc. of ether. Wash the combined ether layer and dis- 
card the aqueous layers. To the ether layer add 50 cc. fifth nor- 
mal aqueous potassium hydroxide and 10 cc. of alcohol and shake 
well, using a moderate circular motion. Repeat the shaking as 
soon as the layers have separated. Separate the layers and 
wash the ether layer with 50 cc. of water containing 5 cc. of 
the aqueous potassium hydroxide and 5 cc. of alcohol. 

Combine the aqueous layers and extract with ether keeping 
all insoluble soaps with the ether layer. Then combine the ether 
layers, transfer to an Erlenmeyer flask, and distill off the sol- 
vent. Take the aqueous layers, acidify with hydrochloric acid 
and extract completely with ether. Transfer this ether solu- 
tion to the “Gums” flask. 

Take the residue and reflux with 25 cc. of alcoholic potash 
for one hour. Evaporate on steam bath until only 10 cc. re- 
mains. Cool, transfer to a separatory funnel with the aid of 
50 ec. each water and ether and shake. Use the same moderate 
circular motion. Repeat the shaking twice and draw off the 
aqueous layer. Extract the aqueous layer with ether again. 
Combine the ether layers and wash twice with 600 cc. portions 
of water. Transfer the ether lavers to the “Gums” flask. Take 
the aqueous layer and the washings from the ether layer, acidify 
with hydrochloric acid and extract completely with ether. Trans- 
fer these ether extracts to a weighed Erlenmeyer flask, distil] 
off the solvent and heat on a steam bath with small portions 
of absolute alcohol until all of the water is removed. Then heat 
to constant weight at 105° C., in an oven filled with carbon 
dioxide. Weigh as fatty acids. 

Take the “Gums” flask, distill off the solvent, remove the 
water, dry and weigh as in the case of the fatty acids. This 
weight is reported as resins or as varnish gums. 


252 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Calculations: 
(a) Wt. of ‘Resins. X: 1.07 < 100—per cent total of resins 
Wt. of sample (direct). 


Wt. of fatty acids 


i rsa le x 100—per cent of total oils. 


(b) 


(c) (Per cent of non-volatile—per cent of ash) =per cent of 
total resins (by difference). 


A method of examining the fatty acids separated from the 
resins in a varnish, as described by de Waele* and by Wolff,; is 
referred to on page 329 of the very valuable book entitled “Var- 
nishes and Their Components,” by R. S. Morrell (Oxford Tech- 
nical Publications). The reader is referred to the original 
papers for a detailed study of the methods. It is believed that 
while occasion may arise for work of this character, as a rule 
much more information regarding the suitability of a varnish 
for a certain purpose can be obtained by practical physical tests, 
as referred to in other sections of this volume. 


EXAMINATION OF SPIRIT VARNISHES 


Distillation of 100 cc. may be made when it is important to de- 
termine the type of solvents used. The distillate can be frac- 
tioned and tested for alcohol benzol, or similar light solvents gen- 
erally employed in such varnishes. Mineral spirits and turpen- 
tine are to be looked for when spirit varnishes of the dammar 
type are believed present. The solvents used in shellac varnish 
and shellac varnish substitutes Manilla Rosin, etc., are generally 
of the alcohol soluble type. 

For a determination of the amount of solvent present in a 
spirit varnish, a quantity can be weighed out in a friction top 
tin cover, evaporated in an oven, and the residue weighed as de- 
scribed elsewhere in this volume for the determination of the 
amount volatile matter in varnishes. The residue left from the 
evaporation may be examined to secure some information re- 
garding the type of resin used. Determination of the solubility 
of the residue in various solvents, determination of the acid 


*de Waele, Journ. Oil Col. Chem. Assoc., 1920, 8°75: 
tH. Wolff, Chem. Age, 1921, 15, 2989. 


ANALYSIS OF VARNISH 253 


value, and similar characteristics, as outlined under the chapter 
for the examination of resin, may afford considerable informa- 
tion. 

Morrell, in commenting upon a scheme for the detection and 
separation of common resins, as published by H. Rebs in “Die 
Spirituslackfabrikation” (1905), makes the following statement: 


Concentrated acetic acid will dissolve lac, rosin, an 
oleoresin of turpentine and accroides resin. Very dilute 
ammonium chloride will dissolve lac, while manila, 
sandarach, rosin, and accroides are insoluble. Benzine 
(light petroleum) will dissolve rosin or an oleoresin, but 
manila, sandarach, lac, and accroides are insoluble in 
that solvent. In order to separate the different resins 
qualitatively and quantitatively in a spirit varnish, the 
solvent is distilled off, the residue is finely powdered and 
warmed on the water bath with the solvents mentioned 
above. If lac and rosin be present, the lac will dissolve 
in very dilute ammonium chloride. Lac may be sepa- 
rated from manila or sandarach, and likewise from 
rosin, but the separation of sandarach from manila 
copal is very doubtful. The estimation of dammar ad- 
mixed with spirit copal or kauri by means of alcohol 
and chloroform has been put forward by Stewart.* 
The resin is boiled with alcohol, which dissolves the 
spirit copal and part of the dammar. The residue is ex- 
tracted with chloroform in a Soxhlet, whereby the re- 
mainder of the dammar is dissolved. The amount of 
the chloroform-soluble extract is a measure of the per- 
centage of dammar. The insolubility of a genuine sam- 
ple of the particular variety of dammar must be known. 

It is evident that the methods of separation of the in- 
dividual resins in a mixture are by no means satisfac- 
tory, and there is need for much investigation in that 
field.t At present the works tests are essentially the 
most reliable. Elasticity, lustre, hardness, uniformity 
of film, and, in the case of coloured spirit varnishes, 
stability to heat and light, are compared against special 
requirements. On metals the varnish film must be 
clean and the coating must not have an acidity likely to 
set up chemical interaction with the metals. Determi- 
nation of acidity, behaviour on drying, flow, colour, and 
specific gravity are compared with corresponding 
values of the standard sample. 

If the spirit varnish contain nitrocellulose celluloid, 
or cellulose acetate, the residue after the removal of the 


* S. Stewart, Journ. Soc. Chem. Ind., 1909, 28, 348. 
+ Dietrich, Analysis of Resins, 2nd Ed. 


254 


EXAMINATION OF PAINTS, VARNISHES AND COLORS 


solvents must be examined by special tests. Treatment 
with a dilute solution of diphenylamine in concentrated 
sulphuric acid will give a blue coloration in the presence 
of nitrocellulose. Nitrocellulose may be estimated in the 
residue by measuring the volume of nitric oxide evolved 
by the action of ferrous chloride and hydrochloric acid 
at 100° C., whereby the nitro-group of the nitrocellulose 
is reduced to nitric oxide. 

Celluloid may be detected by the identification of the 
incorporated camphor, which can be removed by ether 
or by methyl] alcohol, in which the nitrocellulose is in- 
soluble. 

For the detection of cellulose acetate, gentle heating 


‘with concentrated sulphuric acid and a little alcohol will 


give amyl acetate. | 

For the identification of the cellulose component the 
original residue may be boiled with hydrochloric acid 
(s. g. 1.10), neutralised, and tested for the sugars with 
Fehling’s solution. The cellulose in nitrocellulose and 
celluloid can likewise be detected by the production of 
reducing sugars on hydrolysis. 


ae oe wh 


Ce Le ee a ee Se ee ae ee ee ee ee 


Pe EL Oe ee ee ee eT 


ee a ee Ee ee a ee eee ae a ee TS ee ee 


CHAPTER XXIX. 
ANALYSIS OF MIXED DRIERS 


While composed mainly of organic material, mixed driers 
may contain silicon, iron, aluminum, calcium, magnesium, phos- 
phorus, copper, zinc, lead, manganese and cobalt. Some of these 
are present in linseed oil, oils and resins, some may be accident- 
‘ally introduced (as from kettles) and some are purposely added. 
Although the last three only are usually determined, the possible 
interference of the others must be considered in any scheme of 
analysis. 

When an accurate determination of the percentage of various 
metallic driers in oils and varnishes is desired, it is customary 
to slowly ignite the mass and examine the ash. Wet oxidation, of 
such large amounts of sample as are necessary, with nitric and 
sulphuric acids is impracticable and rapid ignition at high tem- 
peratures will result in the volatilization of some or all of ele- 
ments such as lead and zinc. 

The ash is usually extracted with nitric acid, on account of 
the presence of lead. It is to be borne in mind that direct de- 
termination of lead as sulphate is not permissible in the pres- 
ence of calcium, that the bismuthate method for manganese can 
not be used in the presence of cobalt, and that most methods for 
the determination of cobalt require the elimination of several 
of the above constituents. 


RECOMMENDED PROCEDURE* 
(For lead, manganese and cobalt) 


Ash 50-200 g. of the drier in a muffle at the lowest possible 
temperature. Dissolve the ash in dilute nitric acid (1:1), add- 
ing hydrogen peroxide to facilitate solution in case peroxides 
are present. Filter and dilute to measured volume. 

Determine manganese in an aliquot of the above solution by 
the persulphate-arsenite method if cobalt is present and by 
either this method or the bismuthate method in the absence of 
cobalt. (A.S. T. M. Standards, 1921, pages 514-16.) 

Determine lead in another aliquot by first precipitating with 
hydrogen sulphide in a solution of suitable acidity, dissolving 


* Suggested by P. H. Walker. 
256 


256 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


the precipitate in hydrochloric acid with the aid of a little nitric 
acid toward the end, if necessary, and then finally precipitating 
the lead as sulphate or as chromate by the usual procedures. 

Determine cobalt in another aliquot by first evaporating with 
sulphuric acid to eliminate lead, then carrying on a double pre- 
cipitate with ammonia to eliminate iron and aluminum, and 
finally adding potassium nitrite to the combined ammoniacal 
filtrates after acidification with acetic acid. In case the amount 
of cobalt is very small, a preliminary concentration should be 
carried out by treating the ammoniacal filtrates with ammonium 
sulphide, filtering, dissolving the sulphides, making the solution 
alkaline and then proceeding with the acidification and addition 
of nitrite. ; 

If a determination of zinc is desired, it may be carried out in 
the filtrate from the hydrogen sulphide separation of lead. In 
this case, the filtrate should be treated with sulphuric acid and 
evaporated until sulphuric acid is evolved. The cooled solution 
should then be diluted, neutralized until it contains approxi- 
mately one hundredth normal sulphuric acid and zine pre- 
cipitated in the sulphide which can then be ignited and weighed 
as oxide or sulphate. For determining the efficiency of a drier, 
see methods outlined under Interdepartmental Specifications for 
Drier, back of this volume. 

Quick Test for Driers in Varnishes and Pigmented Enamels.— 
A quick test communicated to the writer by C. L. Schumann,* 
for determining such constituents, is as follows: 

Weigh 50 grams of varnish into a 500 cc. Erlenmeyer flask, 
add 60 cc. of denatured alcohol, 60 cc. concentracted hydrochloric 
acid, aud a few glass beads. Heat on a hot plate until most of - 
the alcohol is boiled off. Add about 12 oz. of water and heat to — 
boiling, subsequently filling up to the neck of the flask with tur- 
pentine substitute. Heat and let stand until a clear separation 
is noted. Siphon off the turpentine substitute and add another 
portion thereof. Repeat process. Evaporate the water solution 
to a sufficient concentration for determining metals present. 
This water solution will contain all the metal portion of the 
varnish. The same method as above may be used with enamels, 
but only 2 to 3 grams is required. : 

Morrell+ gives certain qualitative tests for lead, manganese, — 


* Pratt and Lambert Laboratories. 
+ Robert S. Morrell, Varnishes and Their Components. Oxford Technical 
Publications. 


ANALYSIS OF MIXED DRIERS 257 


and cobalt driers in varnish, that are referred to herewith. For 
detecting the presence of lead, the varnish or drier is diluted with 
about an equal quantity of light petroleum ether. A dilute solu- 
tion of potassium bichromate is added, and the mixture shaken 
thoroughly. If lead is present, there will be no sharp line of 
division between the water and the diluted varnish, owing to the 
formation of a precipitate of lead chromate at the dividing sur- 
face, and also on the walls of the test tube. The contents are 
poured out of the tube and the walls carefully examined for the 
presence of yellow lead chromate adhering to the sides. The ad- 
dition of some ammonium sulphide, which will turn the chromate 
to a dark color, is confirmatory. This test works in the presence 
of manganese and cobalt. 

For the presence of manganese, 2 or 3 cc. of the varnish are 
thinned with from 8 to 4 cc. of petroleum ether and shaken for 
about 8 minutes with moderately dilute nitric acid. The aqueous 
layer is withdrawn and boiled with a pinch of manganese-free 

lead peroxide. On settling, a violet color indicates the presence 
of manganese. This test can be performed directly in the pres- 
ence of lead and cobalt. 

For the presence of cobalt, the varnish is diluted with light 
petroleum ether, and then shaken with dilute hydorchloric acid. 
The water layer is separated, and to it there is added an excess 
of ammonium sulpho cyanate with a little concentrated potas- 
sium acetate and 2 or 8 drops of saturated tartaric acid (to re- 
move ferric sulpho cyanate), a blue coloration indicating cobalt. 
If rosin is present, the procedure is slightly modified. 114 ce. of 
the thinned varnish is shaken with 14 cc. of ammonium sulpho 

_ cyanate solution; 14 cc. amyl alcohol, and from 8 to 4 cc. of ether 
‘are added. This mixture is shaken. As a red color might indi- 

‘ cate a trace of iron, 1 cc. of ammonium acetate solution and 2 or 

r 3 drops of saturated solution of tartaric acid are added, whereby 
the varnish-ether-amyl alcohol layer becomes green. The addi- 
tion of 1 cc. of acetone causes a cobalt blue color to appear in the 
aqueous layer. The presence of lead and manganese does not in- 
terfere. 


CHAPTER XXX. 
EXAMINATION AND ANALYSIS OF VARNISH RESINS* 


The value of a resin for varnish purposes depends largely 


upon its physical properties, such as color, hardness, and fusibil- 
ity. In certain cases chemical tests such as acid number and 
acetyl value, yield important information. Knowledge of the 
chemistry of the varnish resins, however, is far from complete 
and their composition, except in two or three cases, is not 
definitely known. Consequently there is much confusion in the 
literature regarding the proper method of procedure for de- 
termining the chemical constants. The purchase of resins on 
chemical constants such as iodine, saponification, and acid values 
together with ash, color, and size of lumps may not be far dis- 
tant. Such procedure would at least eliminate many fanciful 
“gradings” now existing and which have but little meaning. 

All resins used in varnish making may, for analysis at least, 
be conveniently divided into two classes: 

(1) Fossil Resins (“Copals” or “Varnish Gums”). These are 
in general very hard and difficultly soluble. They must be melted 
and held at a rather high temperature until a certain portion is 
driven off and they become soluble in oil. 

(2) Spirit soluble resins such as rosin, sandarac, mastic, 
damar, etc. 

These two groups interlap to a certain extent. For instance, 
Manila which is soluble in alcohol, must be “cracked” at a rather 
high temperature when used in oil varnishes and for the latter 
purpose might be considered as a fossil resin. 


PHYSICAL CHARACTERISTICS OF FOSSIL RESINS 


Hardness.;—The term hardness is purely relative, no definite 
method for determining it having yet been devised.t Moreover, 


* Arranged by the writer and P. C. Holdt, from Scientific Section, Cir- 
cular No. 159. ; 

y+ One of the writers has found valuable for determining the relative 
hardness of resins that may be dissolved in volatile solvents and then 
evaporated to form films, an instrument that will be described in a Scientific 
Section Circular to be printed late in February, 1925. 

¢ An ingenious method has been described by P. Nicolardot and Ch. 
Coffignier, Chimie et Industrie 5150-156-1921. In their apparatus a defi- 
nite weight is applied to a small ball which rests on a piece of the resin. 
The relative hardness of a series of resins is inversely proportional to 
the diameter of the indentation observed when the weight is removed. 


258 


tia of Sk 


259 


ANALYSIS OF VARNISH RESINS 


‘19[}}0g 0} ONp St 91GB, SITYL, 


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*paAlOssip ‘atqn -[es 8 JIM 9ng *paalossip *paajos 
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IIL1IX Fav 


260 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


the value of the resin depends not so much upon its initial hard- 
ness as upon the degree of hardness which it imparts to the fin- 
ished varnish. A resin of greatest initial hardness, however, 
usually produces the hardest varnish. The general scale of 
hardness of the principal types of copal, according to E. J. 
Parry,t is as follows: 


1. Zanzibar 6. Sierra Leone (fossil) 11. Manila 
2. Mozambique 7. Yellow Benguela 12. White Myola 
3. Lindi 8. White Benguela 13. Kauri 
4. Benguela 9. Camaroon 14. Sierra Leone 
5. Pebble 10. Congo (living trees) 


15. South American 


This table agrees fairly well with that of other investigators. 


TABLE XLIV—Table Showing Percentage of Resins Dissolved by Various 
Solvents. By Coffignier 


sd Carbon 
Ethyl Amyl Spirits of * 
Alcohol Ether Alcohol | Turpentine ee 

FRDZADAT Sk oo ats eee a 14.10 | 25.00 | 36.70 | Insoluble Insoluble 
Madagastar a; 2 iN tia 26.20 | 35.00 77.60. 39.70 15.00 
Demersiar see tee 27.90 | 44.60 | 47.00 7.50 24.50 
CONROE oe te ee 74.70) 51.70 45-97 au 31.80 30.90 
pierrs: Leone’. ak ye an 31.10 | 52,20 |} 9620 28 .60 29.10 
Brazile pe ae ae 69.80 | 70.30 | 98.20 51.80 55.10 
Beriguelenik aenzeks tae 83.50 | 56.30 | 99.10 31.20 26.00 

lors) ete 2, Be EN BER os Mn Ora 42.60 | 57.40 | 91.50 20.40 30.10 
Kameritigs st ase ehekas 33.30 | 44.20 | 70.80 21.40 26 .30 
ACDYE. «80th se Ep en et 52.20 | 56.00). 95,90 20.30 19.70 
Kaui; blond) 52 93.40 | 38.20 | Soluble 22.50 18.90 
Kaiti: srowiie ave oe ess 64.20 | 39.30 | Soluble 26.40 22.70 
Kaur. bushi sae es 87.70 | 52.70 | Soluble 27.10 28.10 
Manila, hard, 28. ct. thon 44.10 | 41.50 | Soluble 26.80 31.00 
Manild, triable.) >. Sa Soluble | 71.30 | Soluble 35.90 38 .00 
Pontianads oa.5 ce ee Soluble | 54.00 | Soluble 33.60 38 .09 
Bilne Angolnaarc, sence ak 84.90 | 72.70 | 98.60 30.60 38.70 
RedhAngolic ssi aieaies 62.40 | 48.70 | 93.00 23 .00 22.30 
Colom bis ac7tg4.p sae ee 83.00 | 50.00 | 95.10 31,30 30.40 


According to Bottler, resins may be tested for hardness by 
seratching with rock salt. All are scratched; the hardest only 
with much difficulty. He classifies them in order of decreasing 
hardness: 


1. Zanzibar 5. Congo 
2. Red Angola 6. Manila 
3. Sierra Leone 7. White Angola 
4. Benguela 8. Kauri 


{Gums and Resins, E. J. Parry, Pitman & Sons, London. 


ere rors 


Te ee et, Re ee ee 


ANALYSIS OF VARNISH RESINS 261 


Solubility.—The solubility of the various resins in different 
organic solvents has been thoroughly studied and numerous at- 
tempts made to develop a system of classification based on this 
property. The solubility of a particular resin varies with its 
age, handling after collection, etc. The hardest and best va- 
rieties are in general the most difficultly soluble. Table XLITI, 
XLIV and XLV are taken from K. Dieterich’s “Analysis of 
Resins.” 

Fusibility.—None of the resins have sharply defined melting 
points. The fusing is a continuous process and may extend over 
a considerable range of temperature, as indicated in the table 
below. The harder resins require higher temperatures to melt 
them, and always undergo partial decomposition during the 
melting process. Different samples of the same kind of resin 
often differ considerably in this respect, hence the melting point 
is of little value in identifying a resin. 


TABLE XLV—Due to Coffignier 


Specific Softening | Melting 

Gravity Point Point 
HERI OE ost pos kd 1.058 at16° 65° 165° 
Dribariaiiiven ee ae oe. 16055 atil7> 45° 95° 
PreOLEIrOt Wee ty a 1.066 at 17° 90° 300° 
OCLC SS 0 as ne 1.061 at 17° 90° 195° 
oS eleamser, 0 a or 1.072 at 19° 60° 130° 
ee ek. LUGO ra ZF bal, eae eee 110° 
VE TOSCO: Ce Oa I Oa rr | Gs WIS ALTR eat gid: (OU Sear op ape 150° 
ee emer eo te LeO Ga Alle Coe, ne Ree ee 1202 
rg TCaMe ee 1.065 at 17° 80° 190° 
Diaelanerighle) eae ek we 1.060 at 17° 45° 120° 
Pen ener eee eT 1.037 at 16° 55° 135° 
mally we ca the, wee. 100° 
Bele armen Mer ete ors ey eyelet 2 AD ce ke ue 

300 


Specific Gravity.According to Bottler and Sabin,* specific 
gravity determinations are very useful in estimating the value 
of a resin. The specific gravity of the resin in its usual condi- 
tion and after being freed from contained air is found. The 
resins showing the smallest differences contain the least enclosed 
air and are assumed to be more valuable than their opposites. 
They find that Zanzibar, thus treated at 15° C., gives 1.0621 


*Bottler & Sabin, German and American Varnish Making, John Wiley 
& Sons. Pages 138-14. 


262 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


and 1.0636, the difference being 0.0015. Lindi copal shows a 
difference of 0.0010; red Angola 0.014; Camaroon 0.015; Manila 
0.059; and Kauri 0.064. 

A method for specific gravity suggested by Dieterich for rosin 
and which could be applied to other resins is as follows: 

A series of solutions of common salt, ranging between sp. gr. 
1.070 and 1.085 at 15° C., are prepared, and in each of these is 
placed a few fragments of the colophony under examination, the 
temperature being maintained constant. The sp. gr. of the solu- 
tion which retains the colophony in suspension will be the same 
as that of the substance. In selecting the test pieces, care must 
be taken to reject any which exhibit cracks, air bubbles, or im- 
purities. 7 


CHEMICAL EXAMINATION OF FOSSIL RESINS 


Tschirch and his collaborators, K. Dieterich and others, have 
done a great deal of work on the various resins and have col- 
lected much data concerning their composition, and chemical 
behavior. According to the majority of investigators, varnish 
resins consist largely of resin acids (resinolic acids) and neutral 
substances of unknown composition (designated resenes by 
Tschirch), with small proportions of volatile compounds, ash and 
impurities. The absence of esters, ethers, anhydrides and lac- 
tones (except in the case of rosin) has been fairly well estab- 
lished.* 

According to Tschirch and Stephen, the composition of Zan- 
zibar copal is as follows: trachylolic acid (C,,H.,O,), 80 per 
cent; iso-trachylolic acid (C,,H,.O,), 4 per cent; essential oil, 
9.46 per cent; Alpha-resene (C,,H,,0,) and Beta-resene 
(C,.H,.0,), together 6 per cent; ash .12 per cent; impurities .42 
per cent. Congo copal, according to A. Engel+ has the following 
composition: Congo Copalic Acid (C,,H;,0,.) 48 to 50 per 
cent; Congo-Copalolic Acid (C,,.H,,0,) 22 per cent; Alpha Con- 
go-Copal Resene, 5 to 6 per cent; Beta Congo Copal Resene, 
12 per cent; Ethereal Oil, 3 to 4 per cent; Impurities and Ash, 
4 to 5 per cent. 

For those resins which contain no other saponifiable com- 
pounds than the free resin acids, it might be expected that the 
acid number, determined in the usual manner (i. é., by dissolv- 

* KE. J. Parry, contrary to most other workers, states that all copals 


contain esters. 
+ Journal American Chemical Society, 1903; Vol. 25, p. 860. 


ANALYSIS OF VARNISH RESINS 263 


ing the resin in a suitable solvent and titrating directly with 
KOH solution) would be identical with the saponification num- 
ber. This, however, is not found to be true in practice. The 
saponification number (indirect acid number) is usually con- 
siderably higher than the direct acid number. There are prob- 
ably several contributing causes for this variation. According 
to evidence presented by Worstallt (in a very excellent article on 
Fossil Resins) when a resin is titrated directly with an alkali 
solution, the resin acids are neutralized very slowly. There are 
also indications that small amounts of aldehydes may be pres- 
ent and that these take up alkali during the saponification pro- 
cess, thus giving a higher figure by this method. 

Numerous methods have been proposed for determining acid 
and saponification numbers using different solvents in varying 
proportions. Widely varying values have been reported, and 
much of the literature on the subject is highly contradictory. 
These differences of opinion are undoubtedly due in some cases 
to actual variations in the samples examined, many being of 
doubtful origin. In other cases where there is a wide divergence 
on apparently authentic samples of the same resin, it is probably 
due largely to a difference in the method employed. Hence re- 
ported values are meaningless unless the method used is Spe- 
cifically described. 

Since many of the resins are insoluble or only partially soluble 
in alcohol, it is in general advisable to use other solvents. 
Various mixtures of alcohol, benzine, benzol, ether and chloro- 
form have been suggested. Alcohol alone is suitable only for 
rosin, shellac, and possibly Manila. 

The presence of water in the solution should be carefully 
avoided. It will not mix with most organic solvents, but forms 
an emulsion which makes the titration more difficult by render- 
ing the end point less distinct. Furthermore, according to 
Dieterich, the addition of water decomposes the resin soaps and 
results in abnormally high values. An alcoholic KOH solution 
should always be employed. 

The following methods of analysis have been used and found 
satisfactory by the writers. 

Direct Acid Number.—Weigh three grams of powdered resin 
into a 500 cc. Erlenmeyer flask and add 200 ce. of alcohol benzol. 


{Archive der Pharmacie, 1908, p. 293. 


264 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Allow the mixture to stand overnight in a tightly stopped flask 
and then titrate with fifth normal alcoholic KOH solution, using 
phenol-phthalein indicator. Run a blank on the alcohol-benzol at 
the same time. 

Both the alcohol and the benzol used as solvents should be re- 
distilled before using. The alcohol passing over at 78 to 80° C. 
and the benzol at 80 to 82° C. being collected for the purpose. 

A fifth normal solution of KOH in C. P. absolute Methyl Al- 
cohol is used for both acid and saponification numbers. Methyl 
is preferable to Ethyl Alcohol on account of the difficulty in ob- 
taining the latter sufficiently free from aldehydes to prevent 
darkening on standing. 

Sapontfication Number (Indirect Acid Number).—The same 
quantities of resin and solvent are used as in taking acid number. 
An excess of alcoholic KOH is added, the flask tightly stop- 
pered, allowed to stand 18 hours and then back-titrated with fifth 
normal sulphuric acid. A blank is run on the same quantity of 
alkali and solvent as used in the determination. 

The saponification number may also be determined by boiling 
the resin-solvent-alkali mixture for 14 hour under a reflux con- 
denser. The solution is cooled and the residual alkali titrated as 
before. Saponification numbers determined in this way are 
somewhat higher than those determined by saponification in the 
cold. The solvents and alkali solution for saponification numbers 


are made up in the same manner as those used for Direct Acid — 


Number. 

A method recommended by K. Dieterich and used by Worstall* 
with a slight modification in solvents gives very good results. 
This method is as follows: 

Weigh one gram of the finely powdered resin into a glass- 
stoppered bottle and add 15 cc. benzol and 5 ec. alcohol. Solu- 
tion is complete in a few minutes with these solvents. Then add 
15 ce. fifth normal alcoholic potash solution and allow to stand 
18 hours. Add 25 ec. alcohol and titrate the excess alkali with 
fifth normal sulphuric acid, using phenolphthalein as the indi- 
cator. Blank determinations are run each time. The addition 
of alcohol before the titration is a great help in securing sharp 
end reactions. 

Acetyl Valuwe.—K. Dieterich proposed the following method 
for determining the acetyl value of resins: 


* Journal American Chemical Society, Vol. 25 (1903), page 862. 


— ee a ee or ee | ee 


mR ee ee ee ee ae a  E 


; 
é 
| 


ANALYSIS OF VARNISH RESINS 265 


Boil the resin under a reflux condenser with an ex- 
cess of acetic anhydride and a little anhydrous sodium 
acetate, until completely dissolved, or until it is evident 
that no further portion will pass into solution. Pour 
the solution into water, collect the ensuing precipitate 
and extract with boiling water until perfectly free from 
all traces of uncombined acetic acid. The insoluble 
residues left by copal and dammar are also treated in 
the same manner. The dried acetylized products are 
then tested for the acetyl, acid, ester and saponification 
values by dissolving 1 gram in cold alcohol and titrat- 
ing with half normal caustic potash. The saponification 
is also effected with half normal alkali for half an hour 
under a reflux condenser, and the product titrated back 
after cooling and dilution with alcohol (not water). 
As in the case of fats, the difference between the acetyl- 
saponification value and the acetyl-acid value gives the 
“true acetyl value.” 


Resins Other Than Fossil.—Under this heading are included 
the following types of resins: 

(1) Resins ordinarily used as solutions in some volatile sol- 
vent. Prominent in this group are shellac and macassar which 
are usually applied in alcohol solution and sandarac, mastic, and 
damar, which are generally cut in petroleum spirits, turpentine 
or some similar solvent.+ 

(2) Rosin. 

(3) Ester Gum. 

(4) Synthetic resins. 

These resins are distinguished from the fossil resins in being 
softer, much more readily soluble in volatile solvents and having 
lower melting points. As indicated at the beginning of this chap- 
ter, however, there is no sharp line of demarcation between the 
classes. For example, both manila and macassar might be 
classed either as fossil or as alcohol soluble resins. 

Acid and saponification numbers can be determined by the 
same methods as used for the fossil resins. While most of them 
are soluble to a certain extent in alcohol more concordant results 
will, in general, be obtained when the resin is dissolved in a mix- 
ture of alcohol and benzol.t Alcohol alone is entirely suitable as 
a solvent only for rosin, shellac and macassar. 


+ Manila might also be placed in this class as it is soluble in alcohol and 
is frequently so used. 

t Sandarac is practically insoluble in benzol. For analytical purposes 
hot absolute alcohol is the best solvent. 


266 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Macassar, Sandarac, Mastic and Damar.—These resins are 
usually evaluated entirely on a basis of color, solubility, size of 
lumps and freedom from dirt or other foreign material. How- 
ever, chemical tests such as the determination of acid number are 
of value in checking up on the uniformity of different shipments. 

Shellac (see Chapter XX XI). 

Ester Gum.—The main consideration in the evaluation of ester 
gum is, as a rule to secure the lowest possible acid number con- 
sistent with good color. Determination of melting point and the 
degree of darkening occuring during melting are also important 
indications of quality. 


Cumaron Resin and Synthetic Phenol Resins.—Ellis* refers to the de- 
tection of cumaron resin when mixed with other resins in varnishes 
pointing out that cumaron resin dissolves completely or almost completely 
in acetone. Phenol aldehyde resins are insoluble in petroleum spirits, while 
cumaron resin is partially soluble therein. Phenol aldehyde resins yield 
quantities of phenols on treatment with soda lime, while cumaron resins 
yield only traces of these bodies. Natural resins generally have a high 
acid number, thus differentiating them from the ordinary synthetic resins. 
Separation of cumaron resins from fatty acids is accomplished by esteri- 
fication, the esters being sufficiently removed by distillation or extraction 
with alcohol. Further identification of the resins may be made by de- 
structive distillation, cumaron resin decomposing at about 800° C., with the 
formation of cumarine, iodine, etc. 

Qualitative tests for cumaron resin may be made by color reactions with 
bromine, cumaron resin giving a permanently red color when treated with 
bromine dissolved in chloroform, in the presence of glacial acetic acid. 
Ellis’ method of conducting the test is to use 1 cc. of a 10% solution of the 
resin in chloroform, subsequently diluting with 6 cc. of chloroform and 1 
cc. of glacial acetic acid. The solution is shaken and 1 ce. of a 10% solution 
of bromine in chloroform is added. The solution is again shaken and al- 
lowed to stand in a covered container, the presence of cumaron resin being 
indicated by a permanent red color. 

Ellis also refers to a method of Steinitzer for the detection of phenol 
formaldehyde resins, stating that when they are boiled with sodium hy- 
droxide solution or heated with soda lime, liberation of phenols results, 
which may be identified by their color reactions. 

Yacca Gum (Red Gum; Gum Accrotiides). This product which is quite 
widely used as a shellac substitute in dark colored compositions, is almost 
entirely insoluble in benzol, mineral spirits, or turpentine. It is readily 
soluble in acetone, ether, and alcohol. Distillation under vacuo generally 
yields a phenol body having a strong phenol odor. 

Analysis of Resin Solutions—Analysis of Solution of Spirit Soluble 
Resins is given in Chapter XXVIII, page 252. 


* Synthetic Resins and Their Plastics. The Chemical Catalog Co., Inc. 


Re Nt ee Se gee ee Pe. ee eee ee a ee 


a ee ee eee 


he Ai 


Vite Siete ets adele bails es 


Te es 2 eee 


Pag et oe 


Bvteore li 


a oY bed 


% 
‘a 


sou 


* 
= 
; 


CHAPTER XXXI. 


TENTATIVE METHOD OF TESTING SHELLAC 
A. S. T. M. Serial Designation: D 29-23 T 
DETERMINATION OF MATTER INSOLUBLE IN HoT ALCOHOL 


(a) Continuous Extraction Method (suitable for all grades 
of lac). 
APPARATUS 


1. The extraction apparatus (Fig 101) shall consist of a wide- 
neck flask in which is suspended a metal return condenser. From 
the lower part of this condenser is hung a siphon tube of 
Knoefler type. The extraction cartridge used for the determin- 
ation shall be cut down to such a size that the top of the cart- 
ridge is just above the upper curve of the siphon. It shall be 
supported on three indentations in the glass so that there will 
be a little space beneath and around the cartridge to permit of 
a free flow of liquid. 


Note.—Any type of siphon extractor where the siphon is continuously 
surrounded by the vapors of boiling alcohol may be substituted for the 
above form of apparatus. 


SOLUTIONS REQUIRED 


2. 95-per-cent Alcohol.—Specially denatured alcohol, U. S. In- 
ternal Revenue Bureau Formula No. 1 or Formula No. 30. 


METHOD 


3. Prepare an extraction cartridge 26 mm. in diameter by 80 
mm. in height (Schleicher and Schull No. 603 or the equivalent). 
Place the cartridge in the extraction apparatus, Fig. 1, and ex- 
tract for 30 minutes with boiling 95-per-cent alcohol. 

Dry in an air bath at 105° C., transfer to a glass-stoppered 
weighing bottle, cool and weigh. Dry to constant weight. A 
number of cartridges can be prepared and kept in glass-stop- 
pered weighing bottles until wanted. Now weigh accurately 5 
g. of the lac in a 100-cc. beaker and dissolve in 75 ec. of boiling 
95-per-cent alcohol by immersing the beaker in a hot water bath 
until all the shellac is dissolved and the wax is in solution. 
Transfer this solution quickly into the weighed extraction 
cartridge, previously wet with hot alcohol, putting the cartridge 


267 


268 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


into a carbon filter tube of suitable size supported in a hot water 
bath (Fig. 2), the outlet tube extending through the bottom of 
the bath allowing the escape of the filtrate. Wash all the residue 
from the beaker into the cartridge with hot 95-per-cent alcohol. 
Put the cartridge in the extraction apparatus (Fig. 101), and ex- 
tract for exactly one hour. | 


Keep the alcohol boiling briskly during the extraction. The 
rate of extraction may be controlled by the use of an electric 
hot-point stove, 6 in. in diameter, and using the full current of 
2.2 amperes at 110 volts. The volume of alcohol in the flask 
should be 125 cc. Protect the flask from drafts. Under these 
conditions the tube should siphon over at least 33 times in 1 
hour. The condenser should be able to return all the alcohol 
volatilized during the vigorous boiling of the contents of the 
flask, the object being to effect the maximum extraction during 
the specified time. 

The weight of the residue insoluble in alcohol thus obtained, 
divided by the weight of the sample, and this quotient multiplied 
by 100 is the percentage of alcohol insoluble matter in the Tac. 

NoTe.—When the determination of alcohol-insoluble matter in bleached 
shellac is required, the sample shall be dried if in the form of bars or 
hanks or ground shellac, as the water present dilutes the alcohol to a point 
where solution may not be complete. It is recommended that in preparing 


shellac for this determination, a separate portion be dried by exposure 
to the air in a thin layer, without the application of heat. 


(6) Gooch Filtration Method (Not Applicable for Stick, Seed 
or Grain Lac and Bleached Shellac). 


SOLUTIONS REQUIRED 


4, 95-per-cent Alcohol.—Specially denatured alcohol, U. S. 
Internal Revenue Bureau Formula No. 1 or Formula No. 30. 


METHOD 


5. Grind a 50-g. sample fine enough to pass a 40-mesh sieve. 
Weigh accurately 2 g. of the sample and transfer to a small 


beaker, heat the shellac with 25 cc. of 95-per-cent alcohol. Pre-— 


pare a Gooch crucible with an asbestos pad in the usual man- 
ner’ and dry it to constant weight. Arrange the crucible for 


“For the preparation of the Gooch crucible see any standard text on 
quantitative analysis for example, Fresenius (Cohn Translation), p. 120, 
1904, or Treadwell-Hall, third edition, Vol. II, p. 26. 


i i 


OT ee TS 


TESTING SHELLAC 269 


filtration by suction and pour sufficient boiling alcohol through 
it to thoroughly heat the crucible. 

Notre.—A cold crucible will congeal the wax and prevent filtration. 

Immediately filter the boiling solution through the crucible, 
using suction, transfer the insoluble material from the beaker 
to the crucible, using a “policeman” if necessary and a wash 
bottle containing hot alcohol until the washings are colorless and 
then wash five more times, nearly filling the crucible each time 
with boiling alcohol. 


NoTE.—It will be necessary to shut off the suction momentarily to fill 
the crucible. 


Wash off any film of shellac on the sides or bottom of the 
crucible with hot alcohol and dry to constant weight in an oven 
at 105 to 110° C. The weight of the residue in the crucible, 
multiplied by 100 and divided by the weight of the sample, is 
the percentage of material insoluble in hot alcohol. 


DETERMINATION OF ROSIN 
SOLUTIONS REQUIRED 


6. Acetic Acid.—99-per-cent glacial acetic acid having a melt- 
point of 14.8° C., free from reducing impurities as shown pies its 
action on a eliveriate in sulfuric acid. 


Notre.—If these requirements are not met the results of the rosin deter- 
mination will be erratic. 


Iodine Monochloride Solution.—Dissolve 13 g. of iodine in a 
liter of acetic acid, using gentle heat if necessary, determining 
the strength by titration with thiosulfate. Set aside 50 to 100 
ec. of the solution and introduce dry chlorine gas into the re- 
mainder until the characteristic color change occurs, and the 
halogen content has been doubled. By titration, ascertain if the 
halogen content has been more than doubled, and if so reduce 
it by adding the requisite quantity of the iodine acetic acid solu- 
tion. A slight excess of iodine does no harm but an excess of 
chlorine must be avoided. 

Chloroform.—Should be chemically pure. 

Sodium Thiosulfate Solution—Dissolve 24.83 g. of the pure 
galt in a liter of cold, boiled, distilled water. Standardize by 
titrating against freshly resublimed iodine. It 1s recommended 
that the resublimed iodine be collected into a glass-stoppered 
weighing bottle and weighed after cooling. 

Starch Solution.—Dissolve 0.2 g. of starch per 100 cc, of water 
and boil. 


270 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


METHOD 


7. Introduce 0.2 g. of ground shellac into a 250 cc. dry bottle 
of clear glass with a ground-glass stopper, add 20 cc. of glacial 
acetic acid and warm the mixture gently on top of a hot water 
bath until solution is complete (except for the wax). A pure 
Shellac is rather difficultly soluble; solution is quicker according 
to the proportion of rosin present. Add 10 ec. of chloroform 
and cool the solution to 21.5 to 22.5° C. The bottles should be 
allowed to stand half immersed in a shallow pan of water, well 
insulated or equipped with a suitable thermostat, at least 30 
minutes at 21.5 or 22.5° C. before the Wijs solution is added. 
Add 20 cc. of Wijs solution (which shall be at a temperature 
of 21.5 to 22.5° C.) from a pipette, having a rather small de- 
livery aperture (about 30 seconds). Close the bottle, place it 
back into the pan of water, and note the time. The bottles must 
be kept half immersed in water at 21.5 to 22.5° C. during the 
one hour that the shellac is exposed to the Wijs solution. Agitate 
the bottles occasionally during that hour. 


Notre.—If a number of samples are being run, at least 5 minutes should 
be allowed between the addition of the Wijs solution. 


After exactly one hour, add 10 ce. of freshly prepared 10-per- 
cent potassium iodide water solution, washing into the bottle 
any Wijs solution on the stopper with the same. Titrate the 
solution immediately with the 0.1 N sodium thiosulfate solution, 
allowing the solution to run in slowly (about 25 to 30 cc.) with 
vigorous shaking until the solution becomes a straw color. Now 
add 15 cc. of freshly prepared starch solution and finish titrat- 
ing. The end point is sharp, as the reaction products of shellac 
remain dissolved in the chloroform; any color returning after 
14 minute or so is disregarded. 

A blank determination shall be run at the same time on the 
reagents. The blank is necessary on account of the well-known 
effect of temperature changes on the volume, and possibly loss 
of strength of the Wijs solution. A sample of pure shellac of 
known iodine value should also be run with every set of tests 
on unknown samples. 

In the case of grossly adulterated samples, or in the testing 
of pure rosin, it is necessary to use, instead of 0.2 g. of material, 
a smaller amount (0.15 g. or 0.1 g.) in order that the excess of 
iodine monochloride may not be too greatly reduced, since the 
excess of halogen is one of the factors in determining the amount 


De a Ee Ee eT ae ae ee 


ee ee ee ee ee, ee 


Nall 1 ea Nal al 


TESTING SHELLAC 271 


of absorption. In case less than 25 cc. of the thiosulfate solution 
are required, another test should be made, using a smaller 
amount of the shellac to be tested. 

In weighing shellac, some difficulty is at times experienced on 
account of its electrical properties. In very dry weather it may 
be found that the necessary handling to prepare it for weighing 
has electrified it, and it may be necessary to leave it on the bal- 
ance pan at rest for a few minutes before taking the final weight. 

No pure shellacs show a higher iodine absorption than 18. As 
pure shellac is relatively a high-priced material and as the 
variation between its highest and lowest figures is not great, it 
is recommended that 18 should be taken as the standard figure 
for rosin-free shellac, determined by the method above de- 
scribed. 

The determination for added rosin in bone-dry bleached shellac 
is run the same as above, except that the iodine absorption of 
pure bleached shellac is taken as 10 instead of 18. 

It is recommended that the value for the iodine number of 
rosin be taken as 228. The results of using in this method the 
value of 18 as the iodine number of shellac and 228 as the num- 
ber of rosin, may be that a slightly lower percentage of rosin, 
under some circumstances, will be found than that which is 
actually present. 

The percentage of rosin shall be determined from the formula: 


EMMI UREN OT COE eS ICL AC cc5 iil con nck, Secchccher tesa lbnaMe lets d dee ee 18 
e f ROMP Sti ae, < - ee Pya ee a ag renee oe 228 
ae - BOTTA KUNA VC) oh eee Fe ta al Ao uu ae es eR ig 1 
(«2 — 18) ee , 
(228 — 18) < 100 = percentage of rosin 
lodimesniumber of, bleached: shellac... 2 10 
at : EE COLT E Se fk le tk I ak eS Rie ee 228 
_ ‘ BePINISLUPOr ee se ee ee eet oe ae ets eae Ay 
(2 — 10) 


(228 —10) x 100 = percentage of rosin 


DETERMINATION OF MOISTURE IN SHELLAC 


8. Both orange and bleached shellac give off volatile matter 
at temperatures approaching 100° C. Bleached shellac alters 
chemically at these temperatures, losing its solubility in alcohol. 
For these reasons the usual methods of determining water by 
heating in the air bath at 100 to 110° C. are not applicable in 
the analysis of shellac. 


212 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


SAMPLING 


9. Bleached shellac is sold in three forms: as hanks or bars 
containing approximately 25 per cent of water, as ground 
bleached in pulverized form with about the same water content, 
and as bone-dry or kiln-dried shellac. The latter is prepared 
by drying the ground bleached shellac in the air or in vacuum 
driers at moderate temperatures. It may contain, depending 
upon the completeness of the drying and weather conditions, up 
to 10 per cent or more of water. 

10. Bone-Dry Shellac.—In sampling bone-dry bleached shellac 
about 1 lb. should be taken from different parts of the barrel 
and finely ground by running through a coffee mill. No attempt 
must be made to sieve it. It is rapidly mixed and transferred 
to a Mason jar provided with a screw cap and rubber ring seal. 


The jar should be filled not more than two-thirds full, leaving — 


room for a thorough mixing by shaking the contents. It shall 
be kept in a cool place and tested as promptly as possible. If 
too warm the shellac may become partially solidified, in which 
case the lumps must be broken up by shaking the bottle. 

11. Bars or Hanks.—In sampling bars or hanks it is recom- 
mended that a whole hank be taken. It is crushed and ground 
as rapidly as possible. : 

12. Ground Bleached Shellac_—Ground bleached shellac may 
be treated as above, bearing in mind that the large amount of 
moisture present makes rapid handling imperative. 


METHOD 


13. Bone-Dry.—Weigh 5 g. of the finely ground sample in a 
flat-bottomed dish about 4 in. in diameter and place the dish in 
a well-ventilated air bath from three to six hours at 38 to 43° C. 
One or two electric light bulbs provide a convenient source of 
heat. The temperature should not be allowed to rise above 
AB oC 

NOTE.—With poorly ventilated ovens the drying may take much longer. 


Completeness of drying should be ascertained by continuing the treatment 
to constant weight. The standard is 5 per cent of moisture. 


14. Hanks and Ground Bleached.—Proceed ag in Section 13, 
but with this one exception, that the dish and its contents are 
allowed to dry in the air or in a sulfuric acid desiccator over 
night before it is placed in the air bath. The standard is 25 per 
cent of moisture. 


: y 
re 
a 
3 
4 
. 
_ 
of 

: 2 
a 
& 


TESTING SHELLAC ha 


15. Orange Shellac——Proceed as in the case of Section 13. 
Orange shellac contains between 1 and 2 per cent of moisture. 


Direct Method for Rosin in Shellac.—A direct method for de- 
termining the amount of rosin in shellac has long been desired. 
Such a method is being worked out by the Bureau of Standards 
and promises to be very satisfactory. It is based upon the solu- 
bility of rosin in certain light fractions of petroleum hydrocar- 
bons. See the Bureau of Standards Technologic Paper No. 282. 
This petroleum ether method has not superseded the Wijs iodine 
method where a numerical value for percentage of rosin is de- 
sired. It is, however, of great value in determining the adulter- 
ation of shellac varnishes. 


STEELE MODIFICATION OF THE MCILHINEY METHOD FOR THE 
DETECTION AND ESTIMATION OF ADULTERANTS IN 
SHELLAC VARNISH 


Petroleum ether distilling between 55 and 75° C.* was ob- 
tained by the distillation on the steam bath of either commercial 
petroleum ether or aviation gasoline, fighting grade.+ Glacial 
acetic acid was diluted with water until its solidification point 
was between 13 and 14° C. 

Method.—In case of a shellac varnish, determine the percent- 
age of nonvolatile matter. Place a portion of the well mixed 
sample in a stoppered container. Weigh the container and 
sample. Transfer a weight of the sample corresponding as 
closely as practicable to 2 g. of nonvolatile matter to a 2-liter 
Florence flask, the neck of which has a volume of over 
100 cc. and restopper the container. Weigh the container 
again and by difference calculate the exact weight of the 
portion transferred to the flask. Calculate the exact weight of 
Shellac in the sample taken from the percentage of nonvolatile 
matter in the varnish. The procedure from this point is the 
same for dry and cut shellac. Add 20 ce. of the special acetic 
acid and. heat the flask until the shellac resin and wax are dis- 
solved. With certain shellac adulterants there may be a small 
amount of resin which can not be dissolved. Cool the flask to 
room temperature (19-21° C.), whereupon a part of the natural 


* A fraction with initial boiling point of 40° C. should be satisfactory, 
provided it is not used in extremely hot weather. 
+ Bureau of Mines Technical Paper No. 323, p. 1. 


274 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


shellac wax usually separates. Add slowly from a pipette 50 
cc. of the petroleum ether cooled to 19-21° C., with constant 
shaking of the flask, allowing one to two minutes for the addi- 
tion. Add all at once from a graduated flask 100 ce. more of 
the petroleum ether kept at 19-21° C., stopper the flask and 
shake vigorously. While shaking the flask, slowly add tap 
water kept at 19-21° C., until the shellac has separated as an 
amorphous mass. Half fill the flask with water and agitate so 
as to thoroughly wash the ether layer. Add water until the 
petroleum ether layer nearly fills the neck of the flask, cork and 
let the flask stand until the ether layer is free from suspended 
particles. Transfer 100 cc. of the ether layer to a 100 ce. gradu- 
ated flask. It is convenient to fit the large flask with a two-hole 
stopper with tubes arranged like a wash bottle, so that the ether 
solution can be blown into the graduated flask. 

Evaporate the 100 cc. of petroleum ether solution, portion 
wise if necessary, in a small weighed Erlenmeyer flask on a hot 
plate. When the dry point is reached, suck out the residual 
solvent vapors, cool the flask, and weigh. The weight of the 
residue multiplied by 150 and divided by the weight of shellac 
taken is the percentage of “matter soluble in petroleum ether.” 
Dissolve this residue in 25 cc. of a mixture of equal volumes 
of 95 per cent denatured alcohol and benzol (the mixture should 
be previously titrated to a faint pink color with dilute alkali, 
using phenolphthalein as an indicator) and titrate in the cold 
with 0.1 N alcoholic sodium hydroxide with phenolphthalein as 
an indicator. Calculate the acid number of the “matter soluble 
in petroleum ether” (milligams of KOH required for 1 g. of 
petroleum ether residue). Transfer most of the petroleum ether 
layer remaining in the Florence flask to a small beaker or flask 
and evaporate to dryness. Test this residue for rosin by means 
cf the Halphen-Hicks test already referred to. Report a faint 
purple or blue coloration as “faint test for rosin” and a deep 
purple or blue as “decided test for rosin.” 

An examination of the results on many samples tested by this 


method indicate that a large number of the samples of shellac _ 


were free from rosin, as shown by a qualitative test and by an 
iodine value below the arbitrary accepted limit of 18. Such 
samples can probably be safely considered as unadulterated 
Shellacs. These samples of pure shellac, with few exceptions, 


“Se 


TESTING SHELLAC 


275 


yielded values between the limits of 6.0 and 7.0 per cent for ma- 


terial soluble in petroleum ether and acid values for this residue 
between the limits of 60 and 90. 


TABLE XLVI—Suggested Method for Rating Samples of Shellac 


Purity 


Pure. 

Slightly adulterated; probably 1—2 per cent 
rosin, as in ‘‘Superfine”’ 

Suspicious; no adulteration proved. 

Somewhat adulterated; probably a ‘‘T.N.” 
shellac. 

Somewhat adulterated with an adulterant 
other than rosin. 

Badly adulterated; possibly as high as 40 
per cent adulteration. 

Grossly adulterated; possibly no shellac 
present. 


Petroleum Acid number of 
ether soluble Rosin test residue 
percentage 
@usoriess.... | Negative......... BOSONS ace nice: 
ROO). te cook es POSITIVE «cal oc ws May be greater or 
less than 90. 
Hees Os. oes ee WNP ALIVE™s tal) uc ela ce en GOme to whe teak 
OOO. 2 HPOSLULV.G@r artless Generally, but not 
always over 90. 
3101 0 St a Oa INGHAM NE Se AERA ONS See c fy See cee 
B12:0=20:0). =... Positive or nega- |..... olen: See eee 
tive. 
PETE Met ered Osh ce os sles oor | die eae 's Gans teas eigen: 
oa 
& 
’B 
S ——e 
os iy 
| 5 
' N 
eS + 
Se 
H 
! FI 
5 
S : 
5 
§ 
: Ley 
Depression’ 
| ‘ 
ee a 
Extraction Apparatus for Alco- 
hol-Insoluble Matter 
FIGURE 101 


Filtering Device 


Apparatus Used in Testing Shellac A. S. T. M. Method 


CHAPTER XXXII. 
TESTING INSULATING VARNISHES 


Methods for testing the types of insulating varnishes used in ~ 


America have been worked out by a special committee of the 


American Society for Testing Materials. The tentative methods — 


adopted are as follows: 
TENTATIVE METHODS OF TESTING INSULATING 
VARNISHHES. A. S. T. M. 


Serial Designation: D 115-23 T. — 
Issued, 1921; Revised, 1922; 1923 


1. These tests are intended for varnishes which are applied by 


brushing, dipping or spraying, and are primarily for the pur- 
pose of providing electrical insulation. 


Specific Gravity 


2. The specific gravity shall be measured with a pyknometer, 
Westphal balance or with a hydrometer so graduated that the 


specific gravity can be determined to 0.001. The temperature ‘ 
of the varnish shall be not less than 18° C. (64.4° F.) nor more — 


than 22° C. (71.6° F.) and corrected to 20° C. (68° F.) by ap- 
plying a correction of 0.0007 per 1° C. (0.0004 per 72) 


Viscosity 


3. (a) The vicoscity shall be determined with a Stormer or — 


MacMichael viscosimeter and shall be stated in terms of the q 
viscosity of distilled water determined with the same instrument _ 


under the same conditions. The short-tube type of efflux vis- 
cosimeter usually employed for lubricating oils is not acceptable. 
The temperature of the varnish shall be 20° C. (68° F.). 


(6) The report shall include such details as the kind of in-~ 


strument used, the size of the counterweight if a Stormer instru- 
ment is used, or the size of the wire in case the MacMichael in- 
strument is used, etc. 

Flash Point 


4. The flash point shall be determined in accordance with the 


Standard Method of Test for Flash Point of Volatile Flammable — 


276 


en TE ee a ae ee ae, ee 


INSULATING VARNISHES prareye 


Liquids (Serial Designation: D 56) of the American Society for 
Testing Materials.* 


Time of Drying 


5. (a) Specimens for this test shall be pieces of thoroughly 
cleaned, smooth sheet copper or brass about 3 cm. (1.18 in.) wide 
and 20 cm. (7.88 in. long and about 0.127 mm. (0.005 in.) thick. 

(6) The specimen shall be dipped once in the varnish at a 
room temperature of approximately 20° C. (68° F.) and with- 
drawn slowly and uniformly (about 38 cm. (15 in.) per minute). 
The consistency of the varnish shall be first so adjusted by trial 
that, when dry as determined in accordance with Section 7, the 
thickness of the film of varnish on each side of the metal shall 
be between 0.022 mm. (0.0009 in.) and 0.026 mm. (0.001 in.). 
Care shall be taken before dipping the specimens that the var- 
nish has stood in the dipping tank for a sufficient length of time 
to be free from air bubbles. 

6. (a) Specimens of air-drying varnish shall be dried in free 
air at a room temperature of approximately 20° C. (68° F.). 

(b) In the case of baking vanishes, six specimens shall be 
dipped and allowed to drain at a room temperature of approxi- 
mately 20° C. (68° F.) until the varnish is set as indicated when 
the impression left on the surface by pressing lightly thereon 
with a finger will not become obliterated by further flow of the 
material. They are then to be dried in free air in an oven at 
approximately 100° C. (212° F.). At the end of the first 30 min- 
utes, and again at the end of each 10-minute period thereafter, 
one specimen shall be taken from the oven and examined. In the 
case of slow-drying varnishes, this 10-minute period may be 
lengthened at the discretion of the operator. 

7. The varnish shall be considered dry when a specimen will 
not stick to itself when folded and pressed together between the 
thumb and finger at a temperature of approximately 20° C. 
fos i.) 


Dielectric Strength Test 


8. (a) Specimens for the dielectric strength test shall be pre- 
pared by dipping pieces of thoroughly cleaned, smooth sheet cop- 
per or brass about 20 cm. (7.88 in.) square and about 0.127 mm. 
(0.005 in.) thick into the varnish which shall be at the con- 
sistency prescribed in Section 5 (0). 


* 1921 Book of A. S. T. M. Standards. 


278 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


(b) Each specimen shall be dipped twice, as specified in Sec- 
tion 5 (b), once in each direction, in order to give a more uni- 
form thickness of coating. The specimen shall be dried after 
each dip in the same vertical position in which it was dipped. 

(c) Specimens of air-drying varnish shall be dried in free air 
after each dip at a room temperature of approximately 20° C. 
(68° F.) for a period of 600 per cent longer than that deter- 
mined in accordance with Section 7, provided such period does 
not exceed 24 hours. 

(d) Specimens-of baking varnish shall be drained and then 
baked after each dip for a period of 300 per cent greater than 
that determined in accordance with Section 7 provided such pe- 
riod does not exceed 24 hours. 

(e) The final thickness of the film of varnish on each side of 
the specimen shall be between 0.089 mm. (0.0035 in.) and 0.102 
mm. (0.004 in.). 

9. (a) The dielectric strength of the two films of varnish shall 
be determined by applying alternating potential to two circular 
metal disks, 3 cm. (1.18 in.) in diameter and with edges rounded 
to a radius of 0.64 em. (0.25 in.) which are placed in contact 
with the two sides of the specimen directly opposite each other 
and under a pressure of approximately 0.5 kg. (1.1 lb.). The 
potential shall be applied at a low value and gradually raised at a 
rate such that puncture will occur in about ten to fifteen seconds. 
Ten such punctures are to be made at various points selected at 
random on each specimen. In each test the thickness of the films 
of varnish is to be determined as close to the point of puncture 
as practicable. 

Note.—When necessary, in order to get ten punctures, an additional 
specimen should be tested. 

(6) The frequency of the test potential shall be not greater 
than 100 cycles per second, and each part of the testing appa- 
ratus shall have a continuous rating of not less than 2 kva. (pre- 
ferably larger).- The wave form shall be a sine curve as defined, 
and the voltage shall be measured by methods approved by the 
American Institute of Electrical Engineers.* 

(c) The voltage may be controlled by any approved method 
which does not distort the wave from beyond the limits pre- 
scribed above and which does not subdivide the voltage in steps 


* Standards of the American Institute of Electrical Engineers. 


INSULATING VARNISHES 279 


greater than 500 volts. The apparatus shall comply with the 
Standards of the American Institute of Electrical Engineers. 

10. The volts at puncture, the net thickness of insulation and 
the volts per mil of net thickness shall be reported for each of 
the ten tests together with the average maximum and minimum 
volts per mil. 


Water Absorption Test 


11. Specimens similar to those described in Section 8 shall 
be immersed in water at a room temperature of approximately 
20° C. (68° F.) for a period of 24 hours. Upon removal from 
the water, the surface water shall be wiped off and dielectric 
strength tests made immediately as described in Section 9. 

12. The volts at puncture, the net thickness of the insulation 
and the volts per mil of net thickness shall be reported for each 
of the ten tests, together with the average, maximum and mini- 
mum volts per mil. | 

Heat Endurance Test 


18. For the heat endurance test, specimens shall be prepared 
as in Section 8. After removing not less than 1.27 cm. (0.5 in.) 
from one edge of the specimens, the number of strips required 
by Section 14 (a) shall be cut from the same edge, each 1.9 cm. 
(0.75 in.) in width. 

14. (a) After setting as shown by the test indicated in Section 
6 (b), the strips referred to in Section 13 shall be placed in a 
uniformly heated oven in which the temperature is maintained 
at 100° C. (212° F.) within + 5° C. (9° F.). A strip shall be 
removed at the end of 1, 2, 4, 8 and 24 hours respectively and 
every 24 hours thereafter. These, together with the initial strip, 
shall be tested as follows at a room temperature of appoximately 
oy 2G. (68°. EF.) : 

(b) Each specimen shall be bent through 180 deg. over a rod 
0.32 cm. (1% in.) in diameter. The number of hours of baking 
at which first cracking in the insulation occurs shall be noted 
and reported. 

Acid and Alkali Proof Test 


15. The specimens to be used for the test for acid and alkali 
proofness shall be brass rods 1.5 cm. (0.59 in.) in diameter, 15 
em. (5.90 in.) long and carefully rounded at one end to a radius 
of 0.75 cm. (0.295 in.). These specimens shall be dipped three 
times into the varnish, leaving exposed about 3 cm. (1.18 in.) 


280 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


of the rod at the end opposite the rounded end. Each coat shall 
be dried 25 per cent longer than the period determined in Sec- 
tion 7. Three specimens each shall be prepared for the acid and 
alkali solutions. 

16. (a) The three specimens shall be suspended in the acid or 
alkali whose effect it is desired to determine to within 3 ecm. 
(1.18 in.) of the end of the coated portion of the rod and suit- 
able provision made for detecting the change in the electrical 
resistance between the rod and the solution. (Note 1.) 

(6) It is recommended that these tests be made in 10-per-cent 
solutions as follows: 

Sulfuric acid of sp. gr. 1.069 at 60° F. (15.5° C.) or nitric acid 
of sp. gr. 1.056 at 60° F. (15.5° C.) or hydrochloric acid of sp. 
gr. 1.050 at 60° F. (15.5° C.) and sodium hydroxide of sp. gr. 
L145 at 607 (15:5. 

(c) The temperature of the solution shall be kept at approx- 
imately 20° C. (68° F.). 

NoTE 1. A simple method is to connect a voltmeter between each rod in 
turn and one side of a 110-volt direct current circuit, the other side of the 
circuit being connected to the solution through any piece of suitable metal 
suspended in the solution. The resistance will be inversely proportional to 
the deflection of the voltmeter pointer, that is, the smaller the deflection, 
the greater the resistance. Failure of the material will, therefore, be in- 
dicated by a sudden increase in the deflection of the voltmeter pointer. 

17. The resistance between each rod and the solution shall be 
measured once per day and the number of days elapsing before 
breakdown occurs shall be taken as the “proofness” of the var- 
nish. 

Oil Test 


18. For the test for the effect of oil, pieces cut from the speci- 
mens prepared for the dielectric strength test (Section 8) may 
be used after they have been punctured and measured. 

19. The effect of oil on the varnish shall be determined by im- 
mersing the specimens in transformer oil at a temperature of 
100° C. (212° F.) for 48 hours and noting the effect on the var- 
nish as indicated for example, by wiping with a piece of dry 
white cloth. 


NotTe.—Incipient disintegration of the surface of the varnish may some- 
times be detected by examining the oil for turbidity. If a specimen of the 
oil filtered through filter paper can be distinguished from an unfiltered 
sample when the two samples are held in front of a strong light, the oil 
is turbid. 


INSULATING VARNISHES 281 


Draining Test 


(Also known as “Working Viscosity” Test) 

20. A strip of bond paper 0.064 mm. (2.5 mils) in thickness, 
10.2 cm. (4 in.) in width and 50.8 cm. (20 in.) in length, shall be 
immersed in the varnish at a room temperature of approximately 
20° C. (68° F.) up to a line previously drawn across the paper 
a few inches from the top. The paper shall be withdrawn at a 
slow and uniform rate, care being taken that the varnish is free 
from air bubbles. The specimen shall be permitted to drain 
thoroughly at room temperature while suspended in a vertical 
position. It shall then be dried or baked (according to the type 
of the varnish) until dry as determined in accordance with Sec- 
tion 7. 

21. The thickness of the specimen in mils shall be measured 
at points 5.1 cm. (2 in.), 17.8 cm. (7 in.) and 30.5 cm. (12 in.), 
respectively, from the line to which the specimen was immersed. 

22. The thickness of each film in mils at the three points speci- 
fied in Section 21 shall be recorded. The difference between the 
thickness at the upper point (5.1 cm.) and that at the lower 
point (30.5 cm.) shall be taken as a measure of the variation in 
the film thickness caused by draining. 


Evaporation Test 


23. One hundred cubic centimeters of the varnish shall be 
placed in a flat-bottom crystallizing dish approximately 75 mm. 
(2.95 in.) in diameter and 45 mm. (1.77 in.) in height. It shall 
be heated to a temperature of 100° F. (37.8° C.) + 2° F. (1.1° 
C.) for a period of 7 hours, the sample being exposed to still 
air in the open room. 

24. The decrease in volume of the sample shall be taken as the 
evaporation, this decrease being determined by noting the 
amount of water or kerosene that must be added to fill the dish 
to the original level. 

NoTE.—This test is relative only. That is, it is only suitable for com- 


paring one varnish with another when the tests are made simultaneously 
under exactly the same conditions. 


Test for Non-Volatile Matter 


25. A portion of the sample shall be placed in a stoppered bot- 
tle or weighing pipette and weighed. About 1.5 g. of the sam- 
ple shall be transferred to a weighed flat-bottom metal dish about 


282 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


8 cm. (3.15 in.) in diameter, such as the cover of a friction-top 
tin can. The container shall again be weighed and the exact 
weight of the portion of the sample transferred to the weighed 
dish calculated by difference. The dish with its contents shall 
be heated for three hours in an oven maintained at 105 to 110° 
C. It shall then be weighed after cooling. 

26. The ratio of the weight of the residue to that of the orig- 
inal sample expressed as a percentage shall be taken as the per- 
centage of nonvolatile matter in the varnish. 


CHAPTER XXXTIT. 
EXAMINATION OF PYROXYLIN LACQUER COATINGS 


Heretofore but little information has been published on the 
analysis of soluble cotton solutions, with the exception of that 
given by Zimmer.* Additional matter of a later character is pre- 
sented below, including material used by the writer for several 
years and data submitted through the kindness of J. B. Wiesel, 
Dr. I. M. Jacobsohn, and Dr. Hugo Schlatter. 

No comprehensive scheme of analysis has yet been devised 
which may be considered suitable for all types of nitrate 
lacquers. In the analysis of such lacquers, much depends upon 
the experience and ingenuity of the analyst. He must obtain 
clues as to the ingredients present, and must then devise 
methods to suit the particular mixture at hand. The separation, 
identification, and quantitative determination of mixtures of 
organic solvents, particularly those of similar chemical and 
physical properties, e. g., butyl and amyl acetate, and those 
yielding constant boiling mixtures, are very difficult procedures 
for which methods of analysis cannot be devised without a 
definite knowledge of all of the ingredients present in the par- 
ticular lacquer under examination. The experienced analyst 
will find a physical examination of the lacquer of great value in 
obtaining clues as to the identity of the solvent mixture. The 
determination of the specific gravity, viscosity, color, luster or 
dullness upon drying, behavior upon flowing on glass or spray- 
ing on sheet metal, thickness of film obtained, and the detection 
of the various solvents and thinners by odor, will all be of great 
aid to the experienced analyst in judging the probable composi- 
tion of a given lacquer. 

For instance, in testing airplane dopes it is usual to apply five 
coats of the dope by a brush to standard airplane cotton stretched 
tautly upon an open frame. Duplicates are exposed with and 
without a top coating of finishing enamel made either with pig- 
mented dope or pigmented varnish; the latter usually being 
preferable. After three months, the tautness of the cloth, the 
elasticity of the film and the breaking strength of the cotton 


*Zur Analyse der Zapon und Zelluloidlacke. Fr. Zimmer. Kunststoffe, 
8, 823 (1918). Chem. Abs., 8, 582 (1914). 


283 


284 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


cloth, warp and filling, are determined. For exposing panels of 
nitro-cellulose finishes for automobiles the writer uses black iron 
plates and either applies the dope by brush or by spray gun in 
one coat work, exposing duplicates with and without a top coat- 
ing of finishing oil varnish. While this method does not dupli- 


cate the conditions obtaining in the finishing of automobiles, © 


where several coats are applied sometimes over eleo-resinous var- 


nish primers and fillers, it does give a quick indication of the 
durability of different types of dopes that are made for experi- 
mental purposes. 

It is obviously impossible to give in one chapter in this, book 


complete information regarding the examination of all such — 


compounds as might be derived from aliphatic acids. A study of 
such derivatives of alcohols, including the various esters that 
can be produced with formic, acetic, propionic, and other acid 
derivatives, should be made by the reader, of such extended books 
on the subject as Allen’s Commercial Organic Analysis, and 
Lewkowitsch. 

Weight per Gallon Determination.—The pyroxylin solution is 
adjusted to a temperature of 20° C., and weighed in a marked 
cylinder; the weight of the equivalent volume of water at the 
same temperature being previously determined. 


Weight of pyroxylin solution 


Weight of equivalent volume of water Se ie 


Specific gravity x 8.34—Weight per gallon 


Specific Gravity—tThe specific gravity determination is made 
as outlined above or with a pyconometer. The determination 
is made at 15.5° C. 

Viscosity Determination.—For thin solutions—one to six 
ounces—the viscosity is determined by using a water-jacketed 
pipette, which is standardized to deliver 100 ec. of water at 25° 
C. in eight seconds. The number of seconds required for the 
pipette to deliver 100 cc. of the pyroxylin solution at 25° C. is 
the viscosity of pyroxylin solution. Much more accurate deter- 
mination may be made by comparing the solutions poured in 
glass tubes with Gardner-Holdt viscosity standards. 


For all heavy solutions, the viscosity is determined by the steel 


ball method. The viscosity in this method is equal to the number 
of seconds that it takes a steel ball 5/16” in diameter to fall 


— re oes 


EL ual Rit nat oe 


ee a eae Re eT Eee eae EO ee Tee eae 


PYROXYLIN LACQUER COATINGS 285 


through ten inches of the pyroxylin solution at 25° C. A glass 
tube is to be used, which is at least fourteen inches long and 

only one inch wide, and: with the bottom mark of the required 
_ ten inches at least one inch from the bottom of the tube. 

Effect on Metal.—Much information can be obtained regard- 
ing the non-corrosive properties of a clear lacquer or of the sol- 
vents to be used in a lacquer, by evaporating 50 cc. in a brightly 
polished spun copper dish. The presence of free acid in the 
solvent, usually developed by the hydrolysis of the esters, or of 
free acid developed in lacquers from unstable nitrated cotton, 
will cause a green discoloration. The evaporation may be made 
on asteam bath. The residue, if any is present, may be weighed. 

Free Acidity.—Add to 20 gms. of a clear lacquer, with con- 
stant stirring, 40 c. of a neutralized mixture of 50 per cent de- 
natured alcohol and 50 per cent of water. Then add diluted 
neutralized denatured alcohol until all the solids are precipitated 
and the supernatent liquid is clear. This liquid is then decanted 
and the precipitate washed by decantation with a small amount 
of neutralized denatured alcohol. The decanted liquid and 
washings are then titrated with N/10 sodium hydroxide, using 
phenolphthalein as indicator, until a faint pink color persists for 
at least ten seconds. To neutralize the denatured alcohol in the’ 
above procedure, add a few drops of phenolphthalein indicator, 
and then N/10 sodium hydroxide, drop by drop, with constant 
stirring, until a faint pink color appears. 

Pigment Separation.—The separation of pigments from a 
pigmented lacquer is usually a very difficult thing. Even when 
as low as 10 grams of pigmented lacquer are thinned with as high 
as 100 grams of a mixed solvent, and centrifuged for an hour, 
the colloidal nature of the lacquer is often such as to cause some 
finely divided pigments to remain in suspension. Filtering 
through double layers of filter paper will not remove such pig- 
ments, For this reason, it is customary in many instances to 
merely ash at low temperature a 20 gram sample of the lacquer, 
first having gotten rid of the volatile constituents by evapora- 
tion. The residue from ignition may be examined in accord- 
ance with the methods outlined for the examination of pigments 
in other chapters of this book. Zine oxide, lithopone, and 
titanium oxide are, however, the white pigments usually used 
in white lacquers. When Prussian blue is used, it is neces- 
sary to make a nitrogen determination on the residue from 


286 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


evaporation, and then calculate the Prussian blue from the ; 


nitrogen content (see Chapter XLI on blue pigment analysis). 
If this method is used allowance must be made for nitrogen com- 


ing from nitro-cotton present, the amount of which must be de- 4 


termined. Where organic colors are present, such as paranitran- 
iline, toluidine reds, and similar toners, the determination of the 


exact amount of pigment present is almost an impossibility. ~ 


These pigments would be destroyed in a determination of igni- 


tion residue. Because of their very fine subdivision, they usually — 
cannot be removed by centrifuging. One method, however, that % 


can be tried is to add to the colored lacquer sufficient water to 
precipitate the cotton present, which will carry down with it 
the majority of the pigment present. After removal of the 
solvent and water, the mixture of cotton and pigment can be 


dried. The cotton as a rule can be largely extracted with a very : 
light volatile ester such as ethyl acetate. Some pigmented 


lacquers, however, readily yield their pigment content by centri- 
fuging a mixture of 10 grams of lacquer and 100 grams of mixed 


solvent (1/3 ethyl acetate, 1/3 benzol, 1/3 acetone). If the re- — 


moval of the pigment by extraction is successful, the analytical 
procedure should follow that given in Chapter XXXYV. 

Total Solids (Method A).—Evaporate carefully, to constant 
weight, on a friction top can lid, a 5 gm. sample of the lacquer, 
stirring occasionally to break the “skin” which forms at the 
surface upon the evaporation of the solvents. The solid residue 
upon evaporation may consist of pure cellulose nitrate, of mix- 
tures of cellulose nitrate and camphor, or tri-cresyl phosphate, 
or various resinous and oily materials, in the case of clear 
lacquers, or these various ingredients mixed with pigments in 
the case of pigmented lacquers. This method not as accurate as 
method B on account of difficulty of getting rid of last traces of 
solvents. 


Total Solids (Method B).—A sample (5 to 10 grams) is _ 


weighed out as rapidly as possible in a tared aluminum can with 
a tight fitting cover. About 100 cc. of an ether-alecohol mixture 
(2 to 1) is added, and the mixture stirred until a homogeneous 
mass is obtained. The ether-alcohol solution is then brought to 
a boil over a hot plate or a steam bath and 25 ec. of water is 
added very slowly, with continual stirring. The stirring is then 


continued until the solvent is evaporated off. The stirring is es- 


sential, in order to avoid colloidal precipitate. If the precipita- 


ee ee a ae ee ee go ee ee 


PYROXYLIN LACQUER COATINGS 287 


tion is carried out as outlined, a stringy precipitate is obtained. 
A precipitate in this form dries more easily than a lumpy pre- 
cipitate. The solution is evaporated to dryness on a steam bath, 
and then placed in an oven at 100° C. + 1° C. for two hours; 
cooled in a desiccator for a half (14) hour and then weighed. 
Weight of evaporated material in aluminum can x 100 
Weight of sample 
_ If a cloud is formed on the addition of water to the ether-alcohol 
solution, the presence of camphor is indicated. When camphor 
is present, it is necessary to make two or three additions of water, 
evaporating to dryness after each addition in order to drive off 
all of the camphor. The percentage of camphor may be de- 
termined by the refractometer, as given in Allen’s Commercial 
Organic Analysis. The presence of oil in this pyroxylin solution 
is indicated by an oily feel and appearance of the total solids 
residue. The presence of gums is sometimes indicated by the 
dark brown appearance and brittleness of the total solids residue. 
When oils or gums are present, a weighed portion of the total 
solids residue is placed in a paper thimble, and is extracted with 
alcohol-free ether or chloroform in a Soxhlet extraction tube 
for four hours. The ether or chloroform, containing the oils or 
gums in solution, is transferred to a tared beaker and evapo- 
rated to dryness. Increase in weight divided by the weight 
of the sample times 100, gives the percentage of oils and gums 
in the total solids. To identify the oil or gum used, see methods 
of oil and resin analysis, elsewhere in this volume. The acid 
value, iodine number, and saponification number of this residue 
will give much information. 

Volatile Constituents—Distill a sample of approximately 150 
grams of the lacquer, in steam. Add to the distillate sufficient 
sodium chloride to make a 20% solution of the aqueous layer, 
thus “‘salting out” certain of the solvents and thinners. Separate 
the two layers, oily and aqueous. Fractionate the aqueous layer, 
which should contain alcohol and acetone, if present. The 
presence of alcohol can be detected in the higher boiling fraction. 
The oily layer is referred to below for further examination. 

Acetone Content Determination.—The acetone content is de- 
termined by the Messinger Method.* Careful attention should 
be given to details, in order to get accurate results. It should be 


= % total solids 


* Allen’s Commercial Organic Analysis. 


288 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


remembered that some other solvents such as iso-propyl alcohol 
give the iodoform reaction. 

Sulphuric Acid Insoluble-——Equal volumes of 95% sulphuric 
acid and the oily layer secured as under determination of vola- 
tile constituents are placed in a glass-stoppered, graduated 
cylinder. The acid should be added very slowly with continued 
agitation. The mixture is well shaken and allowed to stand 
until there is a complete separation. The volume of the upper 
layer is the amount of distillate insoluble in sulphuric acid. 
These are hydrocarbons such as benzol, toluol, ete. 

Saponification Value.—Duplicate samples of from four to 
seven grams of the “oily layer’? dried over fused calcium chloride 
are weighed into a pressure flask. Fifty cc. of approximately 
normal alcoholic KOH is added. The pressure flask 1s heated in 
an oven at 100° C. for one hour. It is advisable to wrap the 
pressure flask in a towel before placing in the oven, as there is 
danger of explosion. The flask should be shaken three or four — 
times while being heated. A blank determination is made on 
the alcoholic KOH at the same time as the distillate is being 
saponified. The saponified material in the pressure flasks is al- 
lowed to cool, and is then titrated with N-2 HCl, using phenol- 
phthalein as an indicator. One cc. of N/1 alcoholic KOH is 
equivalent to 0.088 grams of ethyl acetate, or 0.1301 grams of 
amyl] acetate. 

If, after deducting the sulphuric acid insoluble portion, the 
saponification number is between 400 and 500, it is probable 
that amyl acetate is the only other constituent of the oily layer. 
However, since butyl acetate is now being used in such lacquers, 
one must not place too much reliance upon the quantitative an- 
alytical data without actually determining the nature of the ester 
present. It must be borne in mind that these analytical data are 
only indictions as to the nature of the materials present. : 

Should the saponification number, however, be above 500, the 
presence of esters of lower alcohols is indicated. It will, there- 
fore, be advisable to fractionate the oily layer to separate these 
esters. The fraction distilling below 85° C. is collected separ- 
ately from that distilling above 85° C. That passing over be- 
low 85° C. is probably composed of ethyl acetate, gasoline, or 
benzol, or mixtures of these substances. In the absence of 
ethyl acetate, this fraction should be completely insoluble in cold — 
concentrated sulphuric acid. The higher boiling fraction is gen- 
erally composed of amyl or butyl acetate, or mixtures of both, 


PYROXYLIN LACQUER COATINGS 289 


contaminated possibly by some free amy] or butyl alcohol. High 
boiling hydrocarbons, such as xylene, are also occasionally used. 
The presence of such hydrocarbons can be best detected by their 
insolubility in cold concentrated sulphuric acid as outlined 
above. 

After fractionating the oily layer, the sulphuric acid insoluble 
portion of each fraction is determined. Saponify each fraction 
by the method above. Deduct from the total amount of each 
fraction the amount of hydrocarbons present before calculating 
the saponification number. This will give an indication of the 
nature and quantity of the esters present. Technical ethyl ace- 
tate, which may be present in the lower boiling fraction, has a 
saponification number of 600-635. 

Distillation Range.—Fifty cc. of the dried oily layer are dis- 
tilled, using a Barrett 200 cc. benzol distillation flask. The 
temperature range at which each ten per cent by volume distills 
is noted. 

Tricresyl Phosphate.—Boil a small portion of the non-volatile 
residue with sodium hydroxide, then acidify. If tricresy] phos- 
phate is present, the odor of cresol will be detected and the 
presence of phosphates may be determined in the solution. 

Qualitative Tests for Benzol_—Qualitative tests are made by 
adding one cc. of water and one cc. of mixed acid (nitric and 
sulphuric) simultaneously to one cc. of the distillate on a watch 
glass. The characteristic odor of nitrobenzol indicates the 
presence of benzol. 

Discussion and Interpretation of Results.—In the total solids 
determination, the best results are obtained when working with 
about one gram dry weight of nitrocellulose. For this reason, 
it is best to take about 5 grams of solution when determining 
the total solids of a 32-ounce solution, while with a solution con- 
taining less nitrocotton per gallon, a larger sample is taken. 

Camphor is usually present in pyroxylin solutions, in which 
scrap celluloid is used as the base, or in pyroxylin solutions when 
a high boiling latent solvent is needed, such as in mantle dips. 
When more than one or two per cent camphor is present, the 
camphor content should be determined by the refractometer. 
Wken analyzing a solution which contains scrap celluloid as a 
base, about 20% of the weight of the nitrocotton, as determined 
by the total solids determination, should be added to the total 
solids determination in order to get the percentage of scrap 
celluloid used. The camphor type of pyroxylin solution is easily 


290 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


recognized after some experience in working with such solu- 
tions, and it is seldom necessary to use the refractometer in 
evaluating the pyroxylin solution. 

In determining whether a low, medium or high viscosity type 
of soluble cotton was used in the solution, the viscosity de- 
termination and the nitrocotton content of the solution are taken 
into consideration. From the weight per gallon determination 
and the specific gravity of the distilled solvent, the ounces of 
nitrocotton per gallon of solution may be determined. 

Soluble cotton ranges in nitrogen content from about 11 to 
12.6 per cent, the former being used for celluloid and similar 
plastics, the latter for smokeless powder. Either of these varie- 
ties or any in between these two extremes may be met with in 
present day lacquers. The nitrogen content (between the limits 
stated) alone is, however, no indication of the suitability of a 
soluble cotton for any particular purpose, nor does it bear any 
direct relation to viscosity or solubility in any particular solvent. 

The saponification determination indicates the presence of any 
esters. Knowing the range of the distillation of the various 
esters, the type of ester present in the distillate may be in- 
dicated from the distillation range of the distillate; and from the 
saponification value, the percentage of this ester in the distillate 
is estimated. The acetone content determination indicates the 
percentage of acetone or ketones present. The sulphuric acid 
insoluble gives the approximate proportion of benzol or benzine, 
and possibly toluol or xylol present. The water soluble layer 
includes all of the denatured alcohol, wood acohol, acetone, or 
ketone present. Some of the esters and acetone oil have also 
a small water soluble. From the above assumptions, the ap- 
proximate composition of the distillate is estimated. The spe- 
cific gravity of this mixture is calculated, and changes are made 
in the approximate composition until the specific gravity of 
the approximate composition compares favorably with the ~ 
specfic gravity of the distillate. The saponification value and 
the acetone content are the most accurate of any of the determin- 
ations made, with the exception of the specific gravity and dis- 
tillation; and in making changes to obtain the correct specific 
gravity, it is not possible to make as many changes in the solvent 
composition of the distillate as it is in the non-solvent composi- 
tion of the distillate. When changes have been made, so that 
the specific gravity of the approximate composition agrees with 
the specific gravity of the distillate, such a solvent mixture is 


Al 


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PYROXYLIN LACQUER COATINGS 


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292, EXAMINATION OF PAINTS, VARNISHES AND COLORS 


made up, and the specific gravity, water soluble, H,SO, insoluble 
and distillation determinations made on this mixture. If the 
analysis. of this mixture does not compare favorably with the 
analysis of the distillate, further changes in the composition 
are made until the two agree. 

From the composition of the distillate, and the percentage of 
nitrocotton, gums, and oils, the composition of the pyroxylin 
solution may be calculated. 

Stability Test for Cellulose Nitrate.—The stability of cellulose 
nitrate is determined by subjecting samples dried at 35-43 C. to 
various temperatures in the presence of potasium iodide paper. 
The stability may be measured in terms of the length of time 
and temperature necessary to discolor the potassium iodide 
paper. Full details as to this method may be obtained in 
Scott’s “Standard Methods of Chemical Analysis.” Other val- 
uable articles on soluble cotton are found in the books entitled 
Nitro-Cellulose Industry, by Worden; Valuation of Pyroxylin 
Solvents and Leather Solutions, by J. R. Lorenz, Oct., 1919, Jour. 
of Am. Leather Chem. Asso.; and Sidney Young’s book on “Dis- 
tillation Principles,” in which methods for analysis of solvent 
mixtures are given. Young also gives on page 261 a simple 
method (modified Messinger method) for determining acetone. 

Materials to Look For in Pyroxylin Coatings.—There is given 
below a list of the more important materials that are used in 
pyroxylin coatings. There have been proposed probably one 
hundred different plasticizers and stabilizers. Those given be- 
low, however, are the most commonly used. 

Solvents: Ethyl, Butyl, and Amyl Acetates, Ethyl Lactate, 
Acetone Oil, Methyl-Ethyl Ketone, Fusel Oil, Ethyl and Methy] 
Alcohols, Butyl Alcohol, Acetone, Benzol, Toluol, Gasoline. 

Plasticizers and Stabilizers: Di-Ethyl Carbonate, Tri-Cresy] 
Phosphate, Di-Ethyl, Phthalate Urea. 

Oils: Castor Oil, Linseed Oil, or Rape Seed Oil usually in 
Blown or Heavy Bodied Form. 

Resins: Copal, Kauri, Pontianac, Manilla, Shellac, Damar, 
Ester Gum and Phenol Colophony or Phenol Formaldehyde, Con- 
densation Resins. 

Cotton: Usually Regular Soluble Nitrated Cotton. Special 
Nitrated Cotton soluble in absolute alcohol also used. 

Pigments: Usually high strength toners, C. P. chemical colors, 
high strength blacks, and finely ground mineral or chemical col- 
ors of greatest hiding power. 


CHAPTER XXXIV. 


BITUMINOUS PAINTS, VARNISHES, CEMENTS AND SIMILAR 
MATERIALS 


During the past five years the use of bituminous substances 
for cold application as protective coatings has increased con- 
siderably. This has resulted in an urgent demand for specifica- 
tions and methods for analyzing and testing them. Heretofore, 
reliable methods have not been available. The following descrip- 
tions and methods, as prepared for this volume by E. F. Berger, 
formerly of the Bureau of Standards, are to be highly recom- 
mended. 

Bituminous compositions for cold application can be divided 
into paints, coatings, varnishes, japans, and plastic cements. 

Bituminous Paints——Bituminous paints are generally mix- 
tures of a bituminous material and a volatile solvent which are 
of brushing consistency and which dry and harden by the evapo- 
ration of the volatile solvent. They may contain mineral filler 
and pigment and small amounts of fatty matter. The term, 
paint, as defined by the A. S. T. M. is, however, misapplied to 
these materials except in the few instances where pigment is 
added. 

Bituminous paints are marketed under various names but the 
most important kinds can be classed as dampproofing and roof- 
ing paints. Dampproofing paints are used almost exclusively 
on masonry and concrete to prevent the absorption or penetra- 
tion of moisture and are rarely exposed to the weather, being 
protected in some manner. The two most common kinds are 
stone backing and plater bond. 

Stone backing is a solution of a bituminous material in a 
volatile solvent used for coating all surfaces except the exposed 
face of cut stone, concrete blocks, etc., to prevent staining, 
efflorescence, or other discoloration of the exposed face. It is 
of heavy brushing consistency, invariably dries to a tough, 
flexible film free from tackiness and which will not chip or flake 
off in handling. They are composed either of asphaltic or coal 
tar materials. 

Plaster bond is a solution of a rather soft bituminous sub- 
stance in a suitable volatile solvent for coating the inside of 


293 


294 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


exterior walls of brick, tile, stone, etc., before plastering to 
prevent staining, etc. Its value as a means of increasing the 
bond between the plaster and the wall is a matter of question. 
Plaster bonds are usually made from asphaltic materials and 
my contain fatty materials, rosin, rosin oil, aluminum stearate 
or oleate or other heavy metal soaps. They are of heavier con- 
sistency than stone backings and dry to soft, flexible films which 
have a tendency to remain permanently tacky or sticky. 

Roofing paints are used for painting metal roofs and for re- 
coating prepared and built-up bituminous roofing. They vary 
in consistency from those which can be applied with an ordinary 
paint brush to those which require a stiff bristle dauber or three 
knot roof brush for application. The former are usually called 
roofing paints and the latter roof coatings. Roofing paints con- 
sist of a bituminous material thinned with a solvent and may 
contain fine mineral filler or pigments. When pigments are 
present, some drying or fatty oil may be used. Roof coatings 
are of heavier consistency than roof paints and contain mineral 
or other filler usually of a fibrous character in the proportion of 
about 5 to 15 parts per 100 parts of finished paint. Their com- 
mon trade name is liquid fibrous asbestos roof coating. Roof 
paints and coatings may be made from either asphaltic or coal 
tar materials. When using them for prepared or built-up roofing 
only asphaltic materials should be applied over asphaltic roofings 
and only coal tar materials over roofings made with coal tar 
materials. 

Occasionally paints are encountered which consist of a bitu- 
minous substance dissolved in carbon bisulphide or carbon 
tetrachloride. These paints are based on the formula given in 
the patent of Pearce & Beardsley. Their chief advantage is that 
they dry rapidly and give relatively thicker dried films than 
paints of the same consistency made with ordinary solvents. 

Bituminous Varnishes.—Bituminous varnishes are mixtures 
of a bituminous material and fatty oil thinned to a suitable con- 
sistency with a volatile solvent which dry partially by the evapo- 
ration of the volatile solvent and partially by the oxidation of 
the fatty oil. The toughness and general characteristics of the 
film obtained from bituminous varnishes are influenced by the 
fatty oil present. Bituminous varnishes may be either long or 
short oil but those most commonly sold are the short oil type with 
about one part of oil to four of bituminous material. Hard 


BITUMINOUS PAINTS 295 


bituminous materials are generally used and include gilsonite, 
hard native and residual oil asphalts, glance pitch, manjak, 
wurtzelite pitch, grahamite, and fatty acid pitches. 

Bituminous Japans.—Bituminous japans are mixtures of bitu- 
minous materials with or without fatty oil and resins and vola- 
tile solvent the drying and hardening of which is brought about 
by baking. The cheaper grades of japan usually consist of a 
bituminous substance dissolved in a solvent, the better grades 
are mixtures of a bituminous substance with fatty acid pitch, 
drying oils, and resins, with or without small amounts of pig- 
ment. Most black insulating varnishes and Brunswick Black 
are of this character. 

Bituminous Plastic Cements.—Bituminous plastic cements are 
mixtures of trowelling consistency of bituminous materials with 
or without fatty oil and volatile solvent and containing about 
15 to 40 parts of filler, generally of a fibrous character, per 100 
parts of cement. They are applied in thick layers and usually 
dry to tough coatings which remain plastic for long periods. 
They are made either from asphaltic or coal tar materials and 
the same precautions should be taken in their use on bituminous 
roofing as with roof paints and coatings. Pine tar, pine tar oil, 
and hard wood tar are sometimes used to improve spreading 
quality and to modify the odor of coal tar materials. 


CONSTITUENTS OF BITUMINOUS PAINTS, VARNISHES. 
CEMENTS, ETc. 

The following materials are generally used in these products, 
although any material entering into the manufacture of oil 
paints, varnishes, etc., is likely to be used. 

(1) Bituminous Materials. 


Petroleum Asphalts Glance Pitch 
Trinidad Asphalt Wurtzelite Pitch 
Bermudez Asphalt Coal Tar Pitch 
Gilsonite Water Gas Tar Pitch 
Grahamite Pine Tar and Wood Pitches 
Manjak Fatty Acid Pitches 
(2) Fatty and Resinous Materials. 
Linseed Oil Castor Oil 
China Wood Oil Rosin 
Cottonseed Oil Fossil Resins 
Rosin Oil 
(3) Driers. 


Any drier used in oil paints and varnishes. 


296 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


(4) Thinners. 


Petroleum Distillates Pine Oil and Pine Tar Oil 
Coal Tar Distillates Carbon Bisulphide 
Turpentine Carbon Tetrachloride 
(5) Fillers and Pigments. 
Asbestos Slate Dust 
Asbestine Silica 
Clay Rag Fibers 
Portland Cement Jute Fibers 
Limestone Dust Paper Pulp 
Gypsum 


METHODS OF ANALYSIS AND TEST 

(A) Volatile and Nonvolatile: 

(1) Materials without filler—Heat a 1.5 to 2 gram sample in 
a tared metal dish at 105° to 110° C. for three hours. The loss 
in weight is calculated as volatile. 

(2) Materials with filler—Heat a 3 to 5 gram sample spread 
out to a thin layer in a tared metal dish at 105° to 110° C. for 
seven hours. The loss in weight is calculated as volatile. 

(B) Separation and Examination of Thinner: 

(1) Low boiling thinners.—Distill 100 grams of the sample 
with steam at a temperature of 130° C., collecting the distillate 
in a separatory funnel. Stop the distillation when 300 cc. of 
water has distilled. When the distillate has separated into two 
distinct layers, draw off the water, and examine the distillate 
for refractive index, specific gravity, soluble in 38 N. sulphuric 
acid, dimethyl sulphate, or by any other tests necessary for its 
identification. If no pigment or filler is present the residue in 
the flask may be dried and used for a testing as in para- 
graph (D). 

(2) High boiling thinners.—Distill 100 grams of the sample 
in a 200 ec. Engler distilling flask at the rate of about one drop 
per second, avoiding overheating, which may crack the bitumi- 
nous material. Collect fractions up to 170° C., and 170° to 
300° C., at which point the distillation is stopped. In most cases 
the thinner will all have distilled at a point below 300° C. and 
the distillation should be stopped when this occurs. The dis- 
tillates are examined as in (1). The residue in the flask is al- 
lowed to cool until vapors are no longer evolved, when it is 
poured out into a suitable container and, if no pigments are 
present, preserved for further testing as in paragraph (D). 


BITUMINOUS PAINTS 297 


(C) Fillers, pigments and free Carbon: 

Separate the fillers, pigments, and free carbon from the 
vehicle by any of the following methods: 

(1) Weigh accurately about 10 grams of the sample into a 
centrifuge tube. Add about 25 cc. of benzol and stir so as to 
break up the sample, then add about 25 cc. more solvent and 
centrifuge until well settled. Decant the supernatant liquid and 
repeat the extraction twice with 50 cc. portions of benzol and 
then with a mixture of equal parts of benzol and carbon tetra- 
chloride until the supernatant liquid is colorless. Dry residue 
in tube at 105° to 110° C. for one hour and weigh. Preserve 
extracts for further examination of vehicle. The insoluble resi- 
due contains the pigment and fillers, and mineral matter occur- 
ring naturally in the bituminous materials (7. e., Trinidad and 
Bermudez asphalts) and free carbon from coal tar pitches. 

(2) Weigh accurately about 5 grams of the sample into a 
small beaker, add 25 cc. of carbon bisulphide or carbon tetra- 
chloride or benzol (if an examination of the vehicle is to be 
made), break up the sample by stirring and allow to stand for 
15 minutes. Filter through a weighed Gooch crucible, prepared 
with a medium thick mat of asbestos, or an Alundum crucible 
using suction if necessary to aid filtration. Wash the residue 
in the crucible until the washings are colorless, dry in air at 
room temperature until the odor of carbon bisulphide has almost 
disappeared, and then for 1 hour at 105° to 110° C. Cool, weigh, 
and calculate percentage of insoluble material. In this method 
if Trinidad asphalt is present some of the fine mineral matter 
may pass through into the extract. This can be determined by 
evaporating the extract, burning off the bituminous matter, and 
weighing the ash obtained. 

(3) Weigh the sample into a paper thimble and extract in a 
Soxhlet or other suitable extractor. 

Examination of “insoluble matter.—The insoluble matter 
(filler, pigment, free carbon) is examined as in the case of oil 
paints, except as follows: 

(1) Fibrous Filler—Examine microscopically for mineral 
wool, rag fibers, jute, paper pulp and asbestos. 

(2) Free carbon from coal tar compositions, in presence of 
mineral matter containing water of crystallization—When the 
filler is asbestos, this method gives satisfactory results. Extract 
about 5 grams of the sample as in “C” and weigh the residue of 
carbon and asbestos. Now burn off the carbon and weigh. 


298 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Increase this weight by 14 per cent to compensate for water 
of crystallization driven off from the asbestos. Calculate per- 
centages of free carbon and asbestos. 

(3) For mixtures of free carbon with asbestos and clay.—The 
following method has been suggested but has not as yet been 
thoroughly investigated: Extract about 5 grams of the sample 
as in “C” and weigh the residue. Ignite the residue in a crucible 
for seven minutes in a current of dry carbon dioxide (using a 
Rose crucible cover) with a flame about 20 cm. high, or in a 
platinum crucible with a tightly fitting cover in a muffle at 
between 950° and 975° C. for seven minutes. Cool and weigh. 
The loss in weight is water of crystallization from the filler. 
Now burn off the carbon, cool, weigh and calculate the loss in 
weight as free carbon. 

(D) Nonvolatile Vehicle: 

Saponifiable or fatty matter may be determined by either of 
the following methods. If no pigment or filler is present, the 
original material may be taken. If pigment or filler is present, 
it should be removed as in (C) and the extract containing the 
nonvolatile vehicle or base should be evaporated to a small 
volume over a steam bath. 

(1) The following method is essentially that given in 
“Asphalts and Allied Substances”—1920, by Herbert Abraham. 

Weigh 5 grams of the original material (or take the evapor- 
ated extract from 7.5 grams of material obtained as in (C)) and 
dissolve in 50 cc. of benzol using heat, if necessary, to aid solu- 
tion. Add 5 cc. of dilute nitric acid (1:1) and boil under a 
reflux condenser for one-half hour to decompose any metallic 
soaps (7. e., driers, etc.). Add 150 cc. of water, boil under a 
reflux condenser, then transfer to a separatory funnel, draw off 
the aqueous layer, and repeat extractions with water until all 
metals are removed. 

To the benzol solution add 30 cc. of a saponifying liquid made 
by dissolving 100 grams of anhydrous potassium hydroxide in 
500 cc. of 95 per cent ethyl alcohol and diluting to 1,000 ec. with 
90 per cent benzol, and boil under a reflux condenser from one- 
half to one hour. 

Pour the mixture while still warm into a separatory funnel 
containing 150 cc. of boiling water and 25 ec. of a 10 per cent 
solution of potassium chloride. Add 250 ce. of benzol, shake 
vigorously, and allow the funnel to rest quietly in a warm place 


BITUMINOUS PAINTS ZA 


until the solvent separates. (If an emulsion forms which re- 
fuses to separate on standing, add 200 cc. of benzol and 100 cc. 
of 95 per cent ethyl alcohol and stand in a warm place over 
night.) Usually three layers are obtained. Draw off the aque- 
ous solution of the soaps as completely as possible and decant 
the benzol layer leaving the intermediate layer in the funnel. 

Extract the aqueous soap solution with 200 cc. portions of 
benzol until the benzol extract is colorless. 

Combine the benzol extracts with the layer obtained from the 
funnel and extract with 100 cc. portions of 50 per cent ethyl 
alcohol. Add the alcohol extracts of the benzol layer to the 
intermediate layer in the separatory funnel and extract with 
benzol until the benzol extracts are colorless. 

Combine the benzol extracts, evaporate, dry at 105° C., and 
weigh as unsaponifiable. 

Combine the aqueous soap and alcohol extracts and acidify 
with dilute hydrochloric acid, warm, and extract with benzol. 
Evaporate the benzol extract, dry at 100° C. and weigh as 
saponifiable. 

(2) The following method (B. S. Circular 104, Recommended 
Specifications for Asphalt Varnish) is more rapid and avoids 
troublesome emulsions. It has not been tried on compositions 
containing very soft petroleum asphalts, Trinidad and Bermudez 
asphalt, or resins, but it gives satisfactory results on mixtures 
of fatty oil with hard petroleum asphalts, gilsonite, wurtzelite 
pitch, and manjak. 

Weigh about 5 grams of the material into a wide-mouthed 
flask (or take the evaporated extract from 7.5 grams of ma- 
terial obtained as in (C)), add 50 cc. of benzol and 5 grams of 
silica sand, and heat under a reflux condenser on a steam bath 
until the material is entirely dissolved. Add 25 cc. of a half 
normal alcoholic caustic potash solution, and 25 cc. of de- 
natured alcohol, and continue boiling under the reflux condenser 
for one hour. Remove the condenser and evaporate the solution 
to dryness. . 

Add to the residue in the flask 50 cc. of distilled water and 
heat until the residue is disintegrated. Filter the water solution 
of the soaps. Repeat this operation with 25 cc. portions of water 
until the residue is completely disintegrated and the wash water 
is clear and colorless. 

Combine the filtrates (the soap solution and washings), 


300 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


acidify with hydrochloric acid, and heat until the fatty acids and 
any emulsified asphalt separate and rise to the top, and the 
water below is clear. 

Cool, transfer to a separatory funnel, and extract three times 
with 50 cc. portions of ether. Combine the ether extracts and 
wash with water until free from acid. Filter the ether extracts 
through paper into a beaker and wash the residue on the paper 
with ether until the washing runs through colorless. Evaporate 
the ether solutions to dryness. 

Add 15 cc. of 95 per cent ethyl alcohol to the residue in the 
beaker and warm on the steam bath. Cool to room temperature 
and filter through paper into a tared flask or dish. Repeat this 
operation with 10 cc. portions of 95 per cent ethyl alcohol until 
the alcohol remains colorless. Finally wash the residue on the 
paper with 95 per cent ethyl alcohol until the washings run 
through colorless. 

Evaporate to dryness on a steam bath and heat for an hour 
in an oven at 105° C. (221° F.). Cool and weigh. From the 
weight of the residue in the flask and the weight of the original 
sample calculate the percentage of fatty matter. 

(Sometimes the residue obtained after saponification and the 
evaporation of the benzol and alcohol from the saponifying mix- 
ture is not completely disintegrated by boiling with water. In 
that case, extract with water until nothing further dissolves and 
then dry. Dissolve in benzol, using heat if necessary, and wash 
the benzol solution several times with water. Heat the washings 
until the odor of benzol has disappeared and add to the soap 
solution before acidifying.) 

Examination of Saponifiable-——The saponifiable obtained as 
above may be separated into fatty and resin acids by method 
of E. W. Boughton, B. S. Tech. Paper No. 65, and may be tested 
for rosin and fatty acid pitch (Test 37b) “Asphalt and Allied 
Substances” by Herbert Abraham—1920. 

Examination of Unsaponifiable—The unsaponifiable should 
be tested for melting point and fixed carbon. In case the 
sample contains no pigment, filler, or saponifiable these tests 
should be made on the nonvolatile obtained as in (A) or in the 
residue from distillation as in (B). 

For asphaltic materials determine the melting point by the 
“Standard Method of Test for Softening Point of Bituminous 
Materials Other Than Tar Products”—D. 36-21, A. S. T. M. 
Standards, 1921, page 739—(Ring and Ball Method). 


Se Se a Se i 7, 
a or te 


eee ee 


BITUMINOUS PAINTS 301 


For tar products determine the melting point by the 
“Standard Method of Test for Softening Point of Tar Products” 
—D. 61-20, A. S. T. M. Standards, 1921, page 743—(Cube in 
Water Method). 

For tar products having melting points above 77° C. (170.6° 
F.) use Cube Method in Air—‘Asphalts and Allied Sub- 
stances,” by Herbert Abraham—1920, page 516. 

Determine fixed carbon on asphaltic materials by method 
given in Journal of American Chemical Society, 1899, Vol. 21, 
page 1116, or “Fixed Carbon in Bituminous Materials, Its Deter- 
mination and Value in Specifications,” by L. Kirschbaum, Eng. 
Contr. 39, 172 (1913). The fixed carbon obtained from common 
asphaltic materials is as follows. 


EEA ge Uo gi ES 0) sa a nr 12 to 14 per cent 
CSE UIVES cai ® ge UGS ole 2 | A ERR pean teaes ee ne ete 9% to 18 per cent 
I Feb aS RLS a) VE Eo en a 15 to 22 per cent 
Ss CNC eels on citlcla te aeatinccettenee anti 13 to 16 per cent 
GPa hg fe 0 cep c) aa bay ane eae ee ee eR Renee ee 10 to 18 per cent 
Toya Qi 5 2 iia Dn nar See ema oD 14 to 20 per cent 
OVE Fie oS NC BA 0 9 gee oem 15 to 25 per cent 
ETE LESS yyy oo RR IR eee os ee cso 30 to 55 per cent 


(E) Tests for the Differentiation of Asphalt and Coal Tar 
Pitch: 

Owing to the prejudice of the buying public against coal tar 
paints and cements, brought about by the use of materials of 
poor quality made from coal tar materials, and the fact that 
some dealers in asphaltic materials are using these failures as 
selling arguments, the analyst is often called upon to prove the 
presence of coal tar materials other than thinners in asphaltic 
products and vice versa. 

The following tests are useful for this purpose: 

(1) Color of solution of nonvolatile in benzol.—Coal tar mate- 
rials usually give a solution with a yellowish or greenish brown 
fluorescence. Asphaltic materials give a brown solution with- 
out fluorescence. The presence of oily constituents in some 
asphalts may at times give a fluorescence that might be mistaken 
for that obtained from coal tar materials. Wood pitches may 
also give a slight fluorescence. 

(2) Free Carbon.—The presence of free carbon indicates the 
presence of coal tar or coal tar pitch. 

(3) Distillation Test.—Weigh into an iron or copper distill- 
ing retort 100 grams of the material under examination. Heat 


302 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


very slowly until distillation begins and then distill off the 
thinner at the rate of about one drop a second. Usually around 
200° C. a point will be reached where the distillate will stop 
coming over and the temperature will tend to drop. At this 
point the thinner is usually all removed. Change the receiver 
and continue distillation so as to crack or destructively distill the 
bituminous material until the temperature reaches 360° C. Note 
the character of the distillate. Asphaltic materials usually give 
liquid distillates of a brown or reddish brown color. Coal tar 
materials usually give solid distillates of orange or reddish color 
or liquid distillates from which crystals tend to separate. The 
character of distillates from mixtures of the two materials 


varies. The presence of fatty oil is recognized by the odor of | 


acrolein. . 

The following tests are made on the cracked distillate: 

(a) Specific Gravity of Cracked Distillate at 25° C.—Cracked 
distillate of asphaltic materials—0.74 to 0.87. Coal tar mate- 
rials—0.98 to 1.07. Cracked fatty oil lowers the specific gravity. 

(b) Sulphonation with 38 N H,SO,. | 

The following amounts of residue are usually obtained: 


Coal Tar Materials... 2 = 0 to 10 per cent 
Water *Gas =TarPitth. =.) 2 ee 0 to 15 per cent 
Asphaltic Materials cc...) min. 80 per cent 
Wood Tar’ Pitches. 2 0 to 5 per cent 
Fatty Acid Pitches and Fatty Oils... 0 to 5 per cent 


(c) Soluble in Dimethyl Sulphate.—This test may be used 
but with caution owing to its unreliability in the case of small 
amounts of either material. 

The distillates from coal tar materials are usually completely 
Soluble in dimethyl sulphate, while those from asphaltic mate- 
rials are about 85 per cent insoluble. 

(d) Anthraquinone Test.—Melt. the distillate if solid or if it 
contains solid particles and take about 5 cc. for examination. 
Cool and add 10 ce. of absolute ethyl alcohol and allow to stand 
until the solids separate. Decant the liquid and dry the solids. 
Dissolve in 45 cc. of glacial acetic acid and boil under a reflux 
condenser for 2 hours. Add drop by drop to the boiling solution, 
a solution of 15 grams of anhydrous chromic acid dissolved in 
10 cc. of glacial acetic acid and 10 ce. of water. Boil under 
reflux condenser for two hours, allow to cool and add 400 ee. 
of cold water, and filter off the precipitated anthraquinone. The 
crystals of anthraquinone are washed with hot water, then a hot 


ee ee ee 


BITUMINOUS PAINTS 303 


1 per cent solution of NaOH, and then with hot water. The 
residue is dried and weighed and the percentage of anthracene 
ealeulated. From 0:25 to 0.75 per cent of anthracene is found 
in coal tars, and correspondingly larger amounts in coal tar 
pitches. 

A qualitative test to identify the crystals consists in boiling 
them with zinc dust and caustic soda solution, whereupon an 
intense red colored solution (Alizarin) is obtained, which de- 
colorizes in contact with the air. 

This test will serve to identify coal tar materials in asphalt 
compositions. 

(4) Diazo Reaction—devised by E. Graefe—‘Distinction be- 
tween Lignite Pitches and Other Pitches,’ Chem. Zeit. 30—298 
— (1906), serves to distinguish those bituminous substances con- 
taining phenolic bodies from those not containing them, as as- 
phalts. It should be made on the original bituminous sub- 
stance. In the absence of coal tar materials, this test will estab- 
lish the presence of wood tars and pitches in asphaltic mixtures 
especially with a positive Liebermann Storch reaction. 

(F) Physical Tests: 

While the foregoing tests will give some information about 
the composition and quality of these materials, and their suit- 
ability for the purpose intended, the following physical tests are 
at times more valuable for determining the adaptability of a 
material for a particular use. 

(1) Time of drying or setting on prepared roofing, metal, 
concrete, etc. 

(2) Heat test at 140° F. 

(3) Exposure test outdoors at angle of 45° to the south for 
periods varying from one week to a month. 

(4) Baking test. 

(5) Toughness. 

(6) Working Properties. 

(7) Resistance to water, lubricating oil, and acids. 

(8) Heat test on smoke stack paint at 410° F. 

(9) Adhesion tests. 


CHAPTER XXXV. 


ANALYSIS OF WHITE PAINT PIGMENTS 


The vehicle having been extracted from the paint under ex- 
amination, by the previously outlined methods, see pages 213 
to 214, the pigment is left ready for analysis. The pigment 
can be readily classified under one of the following heads by its 
color, thus shortening any preliminary examination. Many of 
the colors have a white base which necessitates a determina- 
tion of both the colored portion of the pigment and of any white 
base which may have been used. 

The general analysis of colored pigments is carried out accord- 
ing to the specific method outlined for the individual colored, 
pigments, together with the methods for a composite white 
paint, provided a qualitative examination does not directly 
reveal the identity of the pigment. 

The pigments used in the manufacture of paints are classified 
as follows, in certain instances the trade names being given by 
which the particular pigments are shown. 


WHITE PIGMENTS 
Lead Pigments 


Corroded White Lead—Basic Carbonate of Lead. 
Old Dutch Process White Lead. 
Quick Process White Lead. 
Mild Process White Lead. 
Carter Lead. 


Sublimed White Lead—Basic Sulphate of Lead—Basic Sul- 
phate-White Lead. 
Zine Lead. 


Leaded Zinc. 
Zinc Pigments 
Zine Oxide—Zine White. 


Lithopone — Alabalith — Ponolith — Beckton White—Charlton 
White—Orr’s White. 


Other Opaque White Pigments : 
Titanium Oxide—Titanox. a 


Antimony Oxide. 

Silica Pigments 
Silica—Silex, 
Asbestine—Taleose. 
China Clay—Kaolin—Tolamite. i 


304 


ANALYSIS OF WHITE PAINT PIGMENTS 305 


Calcium Pigments 


Whiting—Paris White—Chalk—Alba Whiting—Spanish White. 
Gypsum—Plaster of Paris—Terra Alba—Agalite. 


Barium Pigments 


Barytes—Barite—Blanc Fixe—Barium Sulphate. 
Barium Carbonate—Witherite. 


RED AND BROWN PIGMENTS 
Red Lead—Orange Mineral. 
Vermillions—Para Reds. 
Ochres—Tuscan Red—Indian Red—Venetian Red. 
Umbers—Siennas. 

BLUE PIGMENTS 

Sublimed Blue Lead. 
Ultramarine Blue. 
American Blue—Prussian Blue—Antwerp Blue—Chinese Blue. 


YELLOW AND ORANGE PIGMENTS 


Chrome Yellow—Lemon Yellow—Medium Chrome Yellow. 
American Vermillion—Orange Chrome—Basic Lead Chromate. 
Orange Mineral. 


GREEN PIGMENTS 
Chrome Green. 
Chromium Oxide. 
Green Earth. 
BLACK PIGMENTS 
Graphite. 
Carbon Black—Bone Black—Lamp Black—Drop Black—lIvory 
Black—Mineral Black. 
Willow Charcoal. 
Black Oxide of Iron. 


CORRODED WHITE LEAD 
Basic Carbonate of Lead—Old Dutch Process White Lead— 
Quick Process White Lead—Mild Process White Lead 

Corroded white lead contains approximately 80 per cent 
metallic lead and 20 per cent carbonic acid and combined water 
with traces sometimes of silver, antimony and other metals. 
This material should approach the composition indicated by the 
formula 2PbCO,.Pb (OH).. 

Total Lead (Gravimetric) —Dissolve 1 gram in 20 cc. of 
HNO, (1:1) in a covered beaker, heating till all CO, is expelled; 
wash off cover, add 20 cc. of H,SO, (1:1) and evaporate to 
fumes of SO,, cool, add about 150 cc. of water and 150 cc. of 
ethyl alcohol; let stand in cold water one hour, filter on a Gooch 


306 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


crucible, wash with 95 per cent ethyl alcohol, dry at 110° C., and 
weigh the PbSO,. Calculate to PbO or to basic carbonate.* 
Instead of determining the lead as sulphate, the sample may be 
dissolved by boiling with acetic acid; then dilute to about 200 ee. 


with water, make alkaline with NH,OH, then acid with acetic — 


acid, heat to boiling and add 10 to 15 cc. of a 10 per cent solution 
of potassium dichromate; heat till the yellow precipitate assumes 
an orange color. Let settle and filter on a Gooch crucible, wash- 
ing by decantation with hot water till the washings are color- 
less, finally transferring all of the precipitate. Then wash with 
95 per cent ethyl alcohol and then ether; dry at 110° C. and 
weigh PbCrO,. (Any insoluble matter should be filtered out 
before preciptating the lead.) Factor .6375 gives lead content. 

Total Lead (Volumetric).—Dissolve 0.5 gram of sample in 
20 cc. of (1:1) hydrochloric acid and 2 grams sodium chloride, 
boil till solution is effected, cool, dilute to 40 ec. and neutralize 
with ammonium hydroxide. Add acetic acid until distinctly 
acid, dilute to 200 ec. with hot water, boil and titrate with am- 
monium molybdate as follows: 

Dissolve 4.25 grams of ammonium molybdate in water and 
make up to one liter. To standardize this solution dissolve 
about 0.2 gram of pure lead foil in nitric acid (pure PbO or 
PbSO, may also be used), evaporate nearly to dryness, add 30 
cc. of water, then 5 cc. H,SO, (sp. gr. 1.84), cool, and filter. 

Drop filter with PbSO, into a flask, add 10 cc. concentrated 
HCl, boil till completely disintegrated, add 15 cc. of HCl, and 
25 cc. of ammonium acetate slightly acidified with acetic acid. 
Acidify with acetic acid, dilute to 200 cc..with hot water and 
boil. Titrate, using an outside indicator of one part of tannic 
acid in 300 parts of water. | | 

It should be noted that when calcium is present, it forms a 
more or less insoluble molybdate, and results are apt to be high. 
With samples containing less than 10 per cent of lead, the lead 
should be precipitated as PbSO,, filtered, redissolved and titrated 
as in the process of standardizing. 

Carbon Dioxide.—Determine by evolution with dilute hydro- 
chloric acid absorbing in soda-lime or KOH solution. Calcu- 
late CO, to PbCO., subtract PbO equivalent from total PbO and 
calculate residual PbO to Pb(OH).. 


* This method of weighing lead sulphate is not accurate in the presence 
of calcium componds. 


ANALYSIS OF WHITE PAINT PIGMENTS 307 


A more simple and efficacious method of determining the car- 
bonic acid content will be found in the following method. 

The method can be used in such cases where the substances to 
be analyzed evolve gases other than carbon dioxide; that is, hy- 
drogen sulphide, sulphur dioxide, or organic matter. The appa- 
ratus used is shown in Fig. 103. A weighed sample of the sub- 
stance is introduced into the Erlenmeyer flask (A). Into flask 


FIGuRE 108 
Carbon Dioxide Apparatus 


(B) is placed a 10 per cent solution of barium chloride, more 
than sufficient to hold the carbon dioxide evolved, and 20 cc. of 
concentrated ammonium hydroxide free from carbou dioxide. If 
sulphides are present, it is sometimes advisable to pass the lib- 
erated gas first through a few c.c. of strong potassium permanga- 
nate. The flask (B) is warmed until completely filled with am- 
monia fumes. Flask (D) is a safety bottle containing the same 
solution as flask (B). Only in rare cases will any trace of the 
carbon dioxide be noticed in the safety flask. After flask (B) is 
completely filled with ammonia vapor, make all connections and 


308 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


allow the hydrochloric acid to drop slowly from the separatory 
funnel into the decomposition flask (A). When effervescence 
has ceased, heat the contents of the flask until filled with steam. 
The delivery tubes and sides of the precipitating flask are then 
washed with boiling water, the flask is filled to the neck, stop- 
pered, and the precipitated barium carbonate allowed to settle. 
Wash thoroughly by decantation, each time stoppering the flask 
to prevent any error from the carbon dioxide present in the air, 
and determine either gravimetrically, by conversion into barium 
sulphate, or volumetrically, by dissolving in standard hydro- 
chloric acid and titrating the excess of acid used with standard 
potassium hydroxide. Calculate the barium found to carbonate 
and the amount of carbon dioxide from the found carbonate. The 
entire operation may be hastened by conducting a brisk current 
of air free from carbon dioxide through the entire apparatus. 

Two rapid volumetric methods for the determination of car- 
bonic acid contents are described in detail by Leon T. Bonser in 
the Journal of Industrial and Chemical Engineering, March, 
1912, page 203, and by H. W. Brubaker in the same journal, 
August, 1912. 

Acetic Acid.*—Place 18 grams of the pigment in a 500 cc. 
flask, add 40 cc. of syrupy phosphoric acid, 18 grams of zinc 
dust and 50 cc. of water. Connect to a straight Liebig con- 
denser, apply heat and distill down to a small bulk. Then pass 
steam into the flask until it becomes about half full of con- 
densed water, shut off the steam and distill down to a small 
bulk—this operation being conducted twice. To the total dis- 
tillate which was collected in a larger flask add 1 cc. of syrupy 
phosphoric acid, connect to a Liebig condenser, using a spray 
trap, and distill to a small volume—about 20 cc. Pass steam 
through till about 200 cc. of water condenses in the distillation 
flask, shut off steam and continue the distillation. These opera- 
tions of direct and steam distillations are conducted until 10 cc. 
of the distillate require only 1 drop of N/10 alkali to give a 
change in the presence of phenolphthalein. Then titrate the 
total distillate with N/10 sodium hydroxide and phenolphthalein 
and calculate the total acidity as acetic acid. It will be found 
convenient to titrate each 200 cc. portion of the distillate as col- 
lected. 

Metallic Lead.*—Weigh 50 grams of the sample into a 400 


* Thompson’s Method, Jour. Soc. Chem. Ind., 24, 487, 1905. 


ANALYSIS OF WHITE PAINT PIGMENTS 309 


ec. beaker, add a little water and add slowly 60 cc. of 40 per 
cent acetic acid and after effervescence has ceased, boil on hot 
plate. Fill the beaker with water, let settle, and decant the 
clear solution. To the residue add 100 cc. of a mixture of 
360 ce. of strong NH,OH, 1080 cc. of water, 2160 cc. of 80 per 
cent acetic acid, and boil until all solution is complete. Fill the 
beaker with water, let settle and decant the clear solution. Col- 
lect residue on a watch-glass, floating off everything but metallic 
lead. Dry and weigh. Result x 2—percentage of metallic 
lead in sample. 


LEAD HYDRATE 


The following method of A. N. Finn (unpublished) gives total 
basicity of a pure white lead: Place 2 grams of pigment in an 
evolution flask, add a little CO.-free water, connect with a 
_ separatory funnel and condenser (Knorr type), add through 
the funnel, finally washing down, 100 cc. of N/4 nitric acid, boil 
and absorb the CO, in a soda lime tube in the usual manner 
(having H,SO, and CaCl, drying tubes in train) and weigh. 
To the solution in the evolution flask, add about 20 cc. of neu- 
tral sodium sulphate solution and titrate with N/4 sodium 
hydroxide solution (carbonate-free), using phenolphthalein. 
CO, is calculated to PbCO,. The amount of N/4 acid corre- 
sponding to the CO, is calculated and deducted from the total 
amount of N/4 acid neutralized by the sample and the differ- 
ence calculated to combined H,O, from which Pb(OH), is com- 
puted. 

Electrolytic Deposition of Lead—lIn samples of pigment 
which contain less than 5 per cent of lead, the lead content may 
be determined electrolytically in a very rapid manner by follow- 
ing the procedure as outlined by Smith* in his Electro-Analysis, 
as follows: 


Twenty cc. of concentrated nitric acid were added to 
a solution of lead nitrate, giving a total volume of about 
125 ce. and acted upon with a current of N.D..,,,—=10 
amperes and 4.5 volts. The rotating electrode 
(cathode) performed 600 revolutions per minute. The 
deposits had a uniform, velvety black color. There was 
no tendency on the part of the deposit to scale off, 
though more than a gram of the dioxide was preci- 
pitated. The time varied from ten to fifteen minutes. 


* Electro-Analysis, Smith: P. Blakiston’s Sons & Co. 


310 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


A platinum dish with sand blasted inner surface was 
used as an anode. 

By using a current of N.D.,,,.=11 amperes and 4 
volts upon a solution of lead nitrate containing 0.4996 
gram of lead or 0.5787 gram of dioxide, the rate of 
precipitation was found to be: 


Ins oI Ues a2 i eee ees 0.4940 gram lead dioxide 
Dn. BO sm Ti tess 2 a co ae ee 0.5708 gram lead dioxide 
In: 1d: mintites rar oe ee 0.5747 gram lead dioxide 
in ?20-sminwtes: ate, es 0.5770 gram lead dioxide 
In 26 ,,ariniu teaser ees ee plone 0.5787 gram lead dioxide 
In BON ates. ce a oe ee 0.5789 gram lead dioxide 


“The maximum time period for a quarter of a gram of metal 
is twenty-five minutes.” See also Interdepartmental Specifica- 
tions in back of volume. 7 


BASIC SULPHATE OF LEAD 
(Sublimed White Lead) * 


* Schaeffer Method. : 2 : ; 
An average approximate analysis of sublimed white lead as 


commercially placed upon the market should show about 78.5 


per cent of lead sulphate, 16 per cent of lead one and 5. 5 per @ 


cent of zine oxide. 
ANALYSIS 
Total Sulphates 


Mix 0.5 gram of the sample with 3 grams of sodium car- 
bonate in a beaker. Treat the mixture with 30 cc. of water and 
boil gently for ten minutes. Allow to stand for four hours. 
Dilute the contents of the beaker with hot water, filter off the 
residue and wash until the filtrate is about 200 ec. in volume. 


Reject the residue. By this reaction all the lead sulphate is — 


changed to carbonate, the sulphate being transposed into sodium 
sulphate, which is found in the filtrate. 

Acidulate the filtrate with hydrochloric acid and add an 
excess af about 2 cc. of the acid. Boil, and add a slight excess 
of barium chloride solution (12 ec. of an 8 per cent solution). 
When the precipitate has well settled, 4 hours or preferably 
over night, filter on an ashless filter, wash, ignite and weigh as 
BaSO,. Calculate the BaSO, to PbSO, by using the factor 2.6, 
when a half gram sample is used. 

Weight of BaSO, x 1.3 equals weight PbSO,. 

On 0.5 gram sample factor BaSO, to PbSO,—2.6. 


ANALYSIS OF WHITE PAINT PIGMENTS Bt 


TOTAL LEAD 


Molybdate Method.t—Dissolve 1 gram of the sample in 100 cc. 
of an acid ammonium acetate solution made up as follows: 


i See TEE AEL YS) ARE 4 (0 A na Lecce: 
Concentrated ammonium hydroxide... 95 cc. 
ria catnnn lb ens Snccspecsesbaguedeubncbseseovingtvennnsoariontc 100 cc. 


Add this solution hot and dilute with about 50 ce. of water. 
Boil until dissolved. 

Dilute to 200 cc. and titrate with standard ammonium molyb- 
date solution, spotting out on a freshly prepared solution of 
tannic acid. 

Ammonium molybdate is a slightly variable salt, but a solu- 
tion containing 8.67 grams per liter usually gives a standard 
solution: 

1 ec. equals 0.01 gram Pb. 


Standardize against pure PbO. Weigh .5 gram pure litharge 
add 30 cc. hot water and 32 cc. (80%) acetic acid. Heat to 
boiling, and when all litharge is in solution add 27 cc. concen- 
trated ammonium hydroxide. Dilute to 200 cc. with hot water, 
boil and titrate, using outside indicator of 1 part of tannic acid 
in 300 parts of water. . 

Bichromate Method.—Treat the sample as above described 
until dissolved. If the solution is not quite clear, filter. Add 
to the filtrate an excess of neutral potassium bichromate solu- 
tion. Boil until the lead chromate has become an orange yellow 
color and stand in a warm place until the precipitate has settled. 
Filter on a Gooch crucible, wash thoroughly, ignite below a red 
heat and weigh as PbCrO,. 

The PbCrO, may be estimated volumetrically by titrating the 
chromic acid present. For this method, dissolve the lead chro- 
mate from off the filter with hydrochloric acid. Wash well and 
determine the chromic acid present with a standard solution 
of ferrous ammonium sulphate, using a dilute solution of potas- 
sium ferricyanide as an outside indicator. The ferrous ammo- 
nium sulphate is made up of such strength that 1 cc. will equal 
exactly 0.00202 gram Fe. Dissolve 14.19 grams C. P. ferrous 
ammonium sulphate in one liter of distilled water. A small scrap 
of aluminum foil in the bottle prevents oxidation. For a one 


+ Modification of Low’s Method. Technical Methods of Ore Analysis, 
Low, p. 149. 


312 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


gram sample dividing the number of cc. of ferrous ammonium 
sulphate used by 4 gives the per cent of total lead. 

Deduct the lead found as lead sulphate from the total lead and 
calculate the residual lead to PbO. 


TOTAL ZINC* 


Boil one gram of the sample in a beaker with the following 
solution: 


A) (| i MMMM 30 cc. 
Ammonium “chloride... 4 grams 
Concentrated hydrochloric Aid... a ccccccscascesssstensteeon 6 cc 


If the sample is not quite dissolved the result is not affected, 
as the residue is lead sulphate or precipitated lead chloride. 

Dilute to 200 cc. with hot water, add 2 ce. of a saturated 
sodium thiosulphate solution and titrate-with a standard solution 
of potassium ferrocyanide, spotting out on a 5 per cent solution 
of uranium nitrate. Calculate the zinc to zine oxide by multi- 
plying by the factor 1.245. 


TOTAL IRON OXIDE 


Determine this constituent as outlined under the Analysis of 
Litharge. 


THE LEAD CONTENTS IN SUBLIMED WHITE LEAD—A 
CALCULATION} 


The composition of sublimed white lead, the basic sulphate 
of lead, has become a most important factor to users of this 
pigment. Both among rubber manufacturers and producers 
of paints, it is being found essential that the contents of lead 
oxide and lead sulphate be known, so that advantage may be 
fully taken of its characteristic properties. This control neces- 
sitates an analysis of the compound in the laboratory. 

In analyzing sublimed white lead by the usual method, it is 
found that the percentage composition can be determined only 
by an analysis entailing lengthy manipulation, in which the 
content of lead oxide is directly dependent upon the accuracy of 
the other determinations, owing to the necessity of estimating 
its percentage by a calculation based upon the percentage of the 


* Low’s Technical Methods of Ore Analysis. 
+ J. Ind. & Eng. Chem., 6, 200 (1914). 


ANALYSIS OF WHITE PAINT PIGMENTS 313 


other constituents present. The steps in the procedure must 
therefore be closely watched for slight inaccuracies at all times. 


As is well known, the average composition of sublimed white 
lead is given as follows: 


Mm arctrem er es 78.5 
RM Meme 8 16.0 
er are CM ee 5.5 


That its composition varies only slightly from the above 
analysis during a long period of time, is shown by its comparison 
with an average of the entire output of the Eagle-Picher Lead 
Company extending over five months’ time an average embrac- 
ing 270 total analyses. 

This average shows the composition to be: 


DG, UNCLES SINS ere anne 76.68 
eqn ere eae ee: fo ee yo P25 
Peer CC 5.19 

99.70 


A slightly higher lead oxide and zinc oxide content and a cor- 
respondingly lower lead sulphate content is found, than in the 
usually stated formula. It shows, however, only slight variation. 
The average total percentage, consisting of lead sulphate, lead 
oxide, and zinc oxide, was found to be 99.70 per cent. The 
remaining 0.3 of a per cent is only rarely determined, and when 
actually sought is found to consist of moisture, occluded gas 
and ash. A definite ratio exists between the total lead content 
and the lead sulphate and lead oxide contents, and advantage 
may be taken of this relation for a rapid and accurate deter- 
mination of the lead constituents in sublimed white lead. 

In order to arrive at the short method for the anaysis which 
is based upon a direct calculation of the lead and zinc contents, 
it is necessary that only the percentage of zinc and lead be deter- 
mined by the methods already described. 

Using the percentages of zine oxide and total lead, together 
with the average total, 99.70 per cent, determined from the 
large number of analyses, the contents of lead oxide and lead 
sulphate are readily estimated by the following calculation: 


314 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Total percentage of lead compounds present equals 99.70 per cent (average) = 
total percentage found of ZnO, PbO and PbSO, less percentage ZnO. 

Total percentage of lead compounds present equals 99.70 per cent (average total) 
minus percentage ZnO. 


Atomic weight lead... ....<.5... 2s) oa 207.1 
Molecular weight lead oxide........., 5. sae 223.1 
Molecular weight lead sulphate..................... 303.1 


As a hypothetical case, we can assume the presence of a 4.70 per cent ZnO and | 


69.00 per cent metallic lead. 


(1) ——————— X % Pb found } — % Pb constituents 
At. wt. Pb. 
a ears 


Mol. wt. PbSO, — mol. wt. PbO 
Mol. wt. PbO 


Mol. wt. PbO 
Ss ate oe en ) — % Pb constituents 
At. wt. Pb 
= % PbSOQ, present 


(2) 


Mol. wt. PbO — Mol. wt. PbSO, 


Mol. wt. PbSO, 


Determining the percentage of lead oxide and lead sulphate present by the above 
formulas we find: 


303.1 
(1) —— X 69.00 } — 95.00 
207.1 


+ = per cent PbO =s150ne 
303.1 — 223.1 


223 .1 
223.1 

(2) | OR 09.00) — 95.00 
207.1 


—_--———-——— = per cent PhSOQ, = farce 
223.1 — 303.1 


303.1 


Therefore by substituting the percentages of lead and zine 
oxide in the following formula which is derived from equation 
(1) the percentage of PbO in the sublimed white lead is easily 
found. The sum of the percentages of zine oxide and lead oxide 
subtracted from 99.7 gives the percentage of lead sulphate. 


Per cent PbO=[1.464 x % Pb — (99.7 — % GnO) YT 219: 


A comparison of the actual results obtained by the complete 
analysis of sublimed white lead and its calculated composition 
shows that the values obtained are concordant. Indeed the only 
essential factors for the short method are accurate determina- 
tions of the lead and zine contents. The removal of several steps 
in the analysis leads to greater accuracy coupled with a con- 
siderable curtailment of time. 


A table of comparisons shows the following concordance of 
results: 


Te Gee 


i ras lg a i LS ee ee Re ce ee 


het i ot aoe 


See ea oe oe eee 


ANALYSIS OF WHITE PAINT PIGMENTS 315 


TABLE XUUVII 


. Lead Lead Zine Total 
No. Analysis sulphate} oxide oxide lead Total 

MEMUOOINICHO. 555 dae sss 79.20 15.28 Bae 68.30 99.72 
vested es... 79.17 TOU. ie et ee Gee tes ooh 

MMP OINDNIGLG og) la is os. 77.74 16.81 sn 68.70 | 99.66 
Riouintede.... ced. et. CL OE AO? O2 iia a reser oo eared Oe ren ce 

oo = COR Gre TS ean a 77.09 16.95 Halo 68.40 99.77 
Ra culated. oS, 76.85 i UP SES Jet ea te iP Me aE a ks Se 

Ber ONINetet ces. oe. ose 80.20 14.66 4.86 68.40 99.72 
: aleuloteis eo. eS 80.15 ee Ot ames ye emer Sr dae oT 

Demee OM pletej 224... ls. S700) a 10 O0t a5. FT pa 70 OO 071 
ain tedaten hi kw. . Keo PAS Va ea 0 Oe te Ca Oe ke, ee ee 

Mee Gomplctess. 77.84 Lad 4.86 69.00 99.80 
Mraleiiistonee oS. 77.69 bE Bs 3 ar CE ea gS) ee a 

PeimeeOINDIGLE a we... 41222 16.20 Gees 67.80 99.63 
A COTUN 7 Ce ea rr 77.41 Who Wel tee ang eae ae ae fe enn ee 

Beep Omnicte ee... 44.19.| 20.21} 5.48 69.40 | 99.79 
Calcnlateds) «22... on o>... 74.00 imate ie eee my ie ET ge ee ek, 

Pee OMpIEtG h) oui ca wok 77.63 15.92 6.23 67.80 99.78 
Menlciulnted foe) lk... ai Al POROU earache re eS oe ge 

Pre OmMvete .0 44 76.05 17.93 5.73 68 .60 99.71 
Soaloniategeri ches) Ss) 76.04 PAGERS acy celle. os ape ema angie me 

MA IMDIELO a cain ss sk 76.98 Lie78 4.98 69.10 | 99.74 
erieiinted ye os she 76.85 EI TU PR eee ene Se ae (ong 


That this method will prove of value will be readily appreci- 
ated by all chemists who have to determine the percentage com- 
position of any basic sulphate of lead, either for the purpose of 
meeting specifications or for accurate control of finished 
products. 

Graphic Analysis of Sublimed White Lead.—In order to escape 
the determination of SO, and at the same time eliminate the 
calculations the accompanying chart was devised by Burton 
Paxton.* The left hand scale of the chart is graduated from 5 
to 10, representing percentage of zinc oxide in the pigment. 
Right-hand scale is graduated from 65 to 70, representing total 
lead in the pigment. The two center scales are graduated in 
terms of lead sulphate and lead oxide. A line drawn across the 
chart connecting any point (a) on the ZnO scale with any point 
(6) on the Pb scale will intersect the center scales at percent- 
ages of lead sulphate and lead oxide contained in pigment having 
a per cent of ZnO and b per cent of Pb. 

To use the chart it is necessary to have percentages of Pb and 


~ * Above method and chart as published by Burton Paxton in Chem. & 
Met. Eng., May 24, 1922. 


316 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


ZnO in the pigment. These may be determined quite rapidly 
by volumetric methods as follows: 

For ZnO.—Boil 1 gram of pigment in 6 cc. HCl, 30 ce. H,O 
and 5 grams NH,Cl. Pigment will not all dissolve, but this has 
no effect on result. Dilute to 250 cc. with hot water, add a few 
drops of 10 per cent sodium sulphite solution and titrate with 
a standard solution of potassium ferrocyanide, using ammonium 
molybdate as an outside indicator. Ferrocyanide solution should 
equal 0.01 gram ZnO per cc. 

For Lead.—Dissolve 1 gram of pigment in acid ammonium 
acetate and dilute to 200 ce. Heat to boiling and titrate hot 
with a standard solution of ammonium molybdate, using tanic 
acid as an outside indicator. Molybdate solution should equal 
0.01 gram of Pb per cc. 

Now lay straightedge across chart connecting percentage of 
ZnO on left-hand scale with percentage of Pb on right-hand 
scale. Intersection of this line with center scales wil] give per- 
centages of PbSO, and PbO. The sum of percentages of ZnO, 
PbSO, and PbO is, for all practical purposes, a constant, 99.7 
per cent. 

Using this chart, it is possible to make an analysis of pigment 
in 10 or 15 minutes. 


See also Interdepartmental Specifications in back of volume. 


LEADED ZINC 


Leaded zinc is a varying compound containing zine oxide and 
lead sulphate, the latter running from 5 to 35 per cent. 

Moisture.—Heat 2 grams at 105° C. for two hours. 

Lead and Zinc.—Determine the lead directly by the volu- 
metric molybdate method and the zinc by the volumetric ferro- 
cyanide method as outlined under Basic Sulphate-White Lead. 

Total Soluble Sulphates.* (In the absence of BaSO,).—Treat 
0.5 gram of the sample with 5 cc. of water, 3 grams of NH,Cl 
and 5 cc. of HCl saturated with bromine; digest (covered) on 
the steam bath about fifteen minutes, add 25 ce. of H,0O, neutral- 
ize with dry Na,CO, and add about 2 grams more. Boil ten to 
fifteen minutes; let settle, dilute with hot water, filter and wash 


* Report of Sub-committee VIII of Committee D-1, Proceedings of 
American Society for Testing Materials, 14, 271-2, 1914. 


ANALYSIS OF WHITE PAINT PIGMENTS 317 


with hot water; redissolve in HCl, reprecipitated as above and 
wash thoroughly with hot water. Acidify the united filtrates 
with HCl and add a slight excess of 10 per cent BaCl, solution. 
Let stand on steam bath for one hour, filter, wash with hot 
water, ignite and weigh the BaSO,. Calculate to SO, (includes 
SO, formed from SO,). 

Total Soluble Sulphate (in the presence of BaSO,).—Treat 
1 gram in a 600 cc. beaker with 10 cc. of H,O, 10 ce. of strong 
HCl, saturated with bromine, and 5 grams of NH,Cl, heat on a 
steam bath in a covered beaker for five minutes, add hot water 
to make about 400 cc., boil for five minutes and filter to separate 
any insoluble material. (A pure pigment should be completely 
dissolved.) Wash with hot water, ignite and weigh the 
insoluble. Remove lead with Na,CO, as above, making a double 
preciptation, acidify, and to the boiling hot filtrate add slowly, 
with stirring, 20 cc. of a 10 per cent BaCl, solution; let stand for 
two hours on the steam bath, filter, wash, ignite, and weigh as 
BaSO,. (Includes SO, formed from SO.,.) 

Soluble Zinc Sulphate.—Boil 2 grams of the sample with 150 
cc. of water and 50 cc. of alcohol for thirty minutes, filter and 
wash with a mixture of alcohol and water (1:3). Heat the. 
filtrate to boiling and expel most of the alcohol; then determine 
SO, by the usual method of precipitation with BaCl,. Calculate 
to ZnSO, and to SO,. 

Sulphur Dioxide Digest 2 grams of the sample with fre- 
quent stirring in 100 cc. of freshly boiled cold water and 5 ce. 
of concentrated HCl; let stand ten to fifteen minutes, add an 
excess of 0.01 normal iodine solution and titrate back with 
0.01 normal sodium thiosulphate solution, using starch indicator. 
Report as SO,. Run blank on reagents and make corrections. 

Calculations.—Report soluble SO, as ZnSO, Deduct ZnO 
equivalent of the ZnSO, from total ZnO and report residue as 
ZnO. Deduct soluble SO, and SO, equivalent to SO, from total 
SO., calculate remainder to PbSO,; subtract PbO equivalent of 
PbSO, from total PbO and report remainder as PbO. See also 
Interdepartmental Specifications in back of volume. 


ANALYSIS OF ZINC OXIDE 


Total Zinc.—Dissolve 0.25 to 0.3 g. in 10 cc. of concentrated 
HCl and 20 cc. of H,O, make alkaline with NH,OH, then acid 
with HCl, add 3 ce. more of concentrated HCl, dilute to about 


318 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


250 cc. with H,O, heat nearly to boiling and titrate with stand- 


ard potassium-ferrocyanide solution. Report as ZnO (Includes — 


Cd). Iron, copper or other interfering substances should be 
first removed. 
Total Soluble Sulphur.—Moisten a 10 g. sample with water, 


add a few drops of bromine and then concentrated HCl, boil — 


to expel bromine. A small strip of aluminum is added and the 
solution heated gently to throw out any lead that may be pres- 
ent. Now filter off the lead and insoluble and wash with hot 
water. Make alkaline with NH,OH, then just slightly acid with 
HCl, heat to boiling and add about 15 cc. of hot barium-chloride 


solution. Let stand several hours (overnight), filter on a 


weighed Gooch crucible, wash well with hot water, dry, ignite 
for five minutes, cool and weigh as BaSO,. Calculate to S. 


Sulfur Dioxide.—Mix 5 g. of sample with 50 ec. of warm 


(freshly boiled and then partly cooled) water to an emulsion and 
pour into a glass-stoppered flask containing 18 ec. of HCl and 
exactly 25 cc. of N/10 iodine solution, stopper and shake until 
all the oxide is dissolved. Titrate the excess of iodine as rapidly 
as possible with N/10 sodium-thiosulfate solution. Use starch 
indicator. Calculate to SO.. | 

Soluble Zinc Sulfate-——Determine as under Leaded-Zinc. 

Lead Oxide Determination by the Breyer-Croll Electrolytic 
Method.—9.330 grams of the sample are dissolved in a 250 cc. 
beaker with 40 cc. of concentrated HNO, and about 100 ce. of 
distilled water. The solution is boiled for a few minutes until all 
red fumes are expelled. Add enough silver nitrate to precipitate 
all chlorides. Electrolyse for two hours, using about 0.5 ampere 
and a solid sheet platinum anode. The solutions are tested for 
lead before turning off the current by raising the liquid in the 
beaker and allowing to continue for twenty minutes. If there 
is no fresh deposit of PbO,, the electrode is washed three times 
with distilled water (current still on). 

After drying one hour at 110° C., the electrode is weighed. 
The weight of PbO, in milligrams divided by 100 gives the per- 
centage of PbO. 


. The above method is satisfactory for routine work on zinc 
oxide. Where a detailed analysis of other impurities is im- 
portant, the following method may be used. 


Ee OL eae oe ae er 


Te Mase ee ee ee 


ANALYSIS OF WHITE PAINT PIGMENTS d19 


Ferric Oxide.—Treat 10 grams with 50 ce. strong HCl, add 
about 1 gram KCl1O,, and boil down to a syrupy consistency. 
Cool, add water and a large excess of ammonia. Allow to stand 
until the ferric oxide separates, and filter; wash with dilute 
ammonia water and then with hot water. Dissolve the precipi- 
tate of ferric oxide in an Erlenmeyer flask with warm dilute 
H,SO,. Wash the filter paper thoroughly with hot water, dilute 
the solution in the Erlenmeyer flask to about 200 cc. and pass 
in hydrogen sulphide for five minutes. Place a funnel in the 
neck of the flask and boil until all H,S is expelled. Cool and 
titrate with dilute KMnO,. A blank determination is carried 
out in a similar manner and the number of cc. of KMnO, re- 
quired to give a pink color is subtracted from the total number 
required on the sample. 

Manganese Oxide.—Treat a 10 gram sample in a 16 ounce 
Erlenmeyer flask with 100 cc. of HNO, (1:3), heat to boiling 
and add a pinch of sodium bismuthate, when the pink color of 
permanganic acid is produced; now add a few cc. of dilute 
Na,S,O, solution to destroy the pink color, and continue boiling 
to drive off all nitrous oxide fumes. Cool thoroughly and add 
50 ce. of a 3 per cent solution of HNO., and a very small pinch 
of sodium bismuthate to restore the pink color again. Filter the 
solution through a Gooch crucible to remove the excess of sodium 
bismuthate, rinsing the flask and Gooch with 50 cc. of 3 per cent 
HNO, solution to which a small amount of sodium bismuthate 
has been added. Now add 10 cc. of ammonium ferrous sulpha%e 
_ solution, and titrate the excess of ammonium ferrous sulphate 
with standard KMnO, whose iron value has been determined. 
One gram of KMn0O, per liter is a convenient strength; and 12.4 
grams of ammonium ferrous sulphate, and 50 cc. strong H.SO, 
to the liter gives a solution which is almost equal to the per- 
manganate solution. A blank determination is carried out in 
exactly the same manner as with the sample of oxide, and the 
difference in the number of cc. of KMnO, required to give a pink 
color with the blank determination and the sample of oxide is 
equal to the amount of MnO present. The manganese value of 
the KMn0O, is calculated from the iron value, according to the 
ratio of Mn : Fe, or 55 : 279.5 or 0.1968 : 1. 

Arsenious Oxide-—Weigh 10 grams of oxide in a 16-ounce 
Erlenmeyer flask, add about 10 grams of FeSO,, place a rubber 


320 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


stopper with an acid delivery tube and an exit tube, which is 
immersed in a beaker containing about 200 cc. distilled water. 
The beaker of water is placed in a pan of cold water, the pan 
having an inlet and overflow. Now add 100 cc. strong HCl 
from the delivery tube, and heat the flask to boiling so as to dis- 
till the arsenic into the beaker of water. Continue boiling until 
about two-thirds of the acid has been distilled, remove from the 
flame, rinse the delivery tube, add 10 cc. strong HCl to th2 
solution in the beaker, warm and pass in H.S to precipitate 
the arsenic, as As,S,. Let stand in a warm place for some time 
and filter in a Gooch crucible, wash the precipitate of As,S, 
with alcohol and then with carbon bisulphide and several times. 
with dilute alcohol. Dry at 105° C. for one hour and weigh. | 
Dissolve the As.S,, in the Gooch crucible with dilute ammonia 
water, wash well with hot water, and dry at 105° C. and reweigh. - 
The loss in weight is As,S,, from which the As,O, may be calcu- — 
lated. See procedure for arsenic, p. 34 Standard Methods of - 
Chemical Analysis, Scott (D. Van Nostrand Co.) Cuprous © 
chloride used in this method. 

Chlorine-—Ten grams of the sample are covered with water’ } 
and 10 ce. of N/10 AgNo, solution, which has been standardized” 
against pure NaCl, added. Forty ec. of concentrated HNO; 4 
are added and the solution boiled until nitrous fumes are re- 
moved. It is then cooled, 5 cc. of ferric nitrate solution (1:6) ~ 
added and the solution titrated to a faint pink with N/10 am- 
monium sulfocyanide (NH,CNS). A blank shall be run with 
the same reagents, to determine the relative strengths of pe 
solutions. 

Acid Insoluble-——A sample of 10 grams is treated with bi 25 
ec. of water and 25 cc. of hydrochloric acid and evaporated ; 
dryness. The residue is taken up with 50 cc. of 1:4 hydrochlor. 
acid and the insoluble filtered off and thoroughly washed wit i 
1:4 hydrochloric acid and then with boiling water. It is further 
washed with hot ammonium acetate solution and again with 
boiling water. The insoluble is then burned off and weighed.. 

Water Soluble Salts —Five grams of the sample are shaken in 
a 500 cc. graduated flask for 10 minutes with 250 ec. of water 
at room temperature. The solution is made up to exactly 500 
ec. and filtered through dry paper. One hundred cc. of fhe 
clear filtrate are measured out, poured into a weighed plat) um 

Ray 


Mie.” a 
be, iw oe 


ANALYSIS OF WHITE PAINT PIGMENTS eae | 


dish and evaporated to dryness on a sand-bath, the contents be- 
ing protected from dust. The residue is dried for one or two 

hours at 110° C., cooled and weighed rapidly. The increase in 
weight represents the water soluble salts. 


ANALYSIS OF LITHOPONE 


ALBALITH, PONOLITH, BECKTON WHITE, STERLING WHITE, 
» SUNOLITH, ETC. 


- This pigment is a chemically precipitated pigment containing 
~pproximately from 69 to 70 per cent barium sulphate, the re- 
unainder consisting of zinc sulphide, with occasional impuri- 
ties of zinc oxide and carbonate. 

, Moisture—Heat 2 grams for two hours at 105° C. 
-* Water Soluble-—Determine as under zinc oxide. 

Insoluble and Total Zinc.—Take 1 g. of the sample in a 200 
ec. beaker, add 10 cc. of concentrated HCl, mix, and add in 
small partions about 1 g. of KCIO,, then heat on the steam 

& until about half of the liquid is evaporated. Dilute with 


: 


: 71.0, add 5 cc. of dilute H,SO, (1:10); boil, let settle, filter, 
» wash, ignite, cool, and weigh the insoluble which should be only 
c°: make a qualitative examination for alumina and silica. 
;The insoluble should be examined under the microscope for 
the presence of natural crystallin barytes. Sample may also be 
_ examined direct. Make filtrate from insoluble alkaline with 
3 NH, OH, acid with HCl, add 8 cc. of concentrated HCl, dilute 
to. about 250 cc. with H,O, heat nearly to boiling and titrate 
with K,Fe(CN), solution as under zinc white. Calculate to Zn. 
Zinc Oxide.—Treat a 4 g. sample of the lithopone for 4 hours 
»Ww? a 200 cc. of 1 per cent acetic acid at room temperature, stir- 
-_ g occasionally. Filter by suction on a double filter paper and 
~ ash with cold water; add to the clear filtrate 13 cc. of concen- 
t ated NH,OH, neutralize with HCl and then add 3 cc. of con- 
centrated HCl in excess. Heat to boiling and titrate with 
K\Fe(CN),, using uranium-acetate solution as an outside indi- 
cator. Calculate to ZnO. Calculate this result to Zn, subtract 
froin total Zn, and calculate the difference to ZnS. (Any 
ZnCO, or ZnSO, is included in the ZnO.) 
‘Zine Sulfide.*—Place 0.5 g. of pigment in evolution flask with 


.* ‘olution Method of W. G. Scott, “White Paints and Painting Ma- 
te _,’ p. 257; see also Blair, “Chemical Analysis of Iron.” 


O22 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


about 10 g. of “feathered” or mossy zinc, add 50 cc. of water; 
insert the stopper carrying a separatory funnel and an exit 
tube. Run in 50 ce. of concentrated HCl from the funnel, having 
previously connected the exit tube to two absorption flasks in 
series; first flask contains 100 cc. of alkaline lead-nitrate solu- 
tion; second flask, 50 cc. of same as a safety device. After all 
of the acid has run into the evolution flask, heat slowly, finally 
boiling until the first appearance of steam in the first absorption 
flask; disconnect, let the lead sulfide settle, filter, wash with cold 
water, then with hot water till neutral to litmus paper and wash- 
ings give no test for lead. The PbS precipitate is dissolved in 
hot, dilute HNO., evaporate to fumes with H,SO, and finally 
weighed as PbSO,. Calculate PbS or PbSO, to ZnS. 

The alkaline lead solution is made as follows: Into 100 
ec. of KOH solution (56 g. in 140 ec. of H,O) pour a saturated 
solution of lead nitrate (250 g. in 500 ec. of H,O) until the pre- 
cipitate ceases to redissolve, stirring constantly while mixing. 
About 3 volumes of the lead solution will be required for one of 
the alkali. 

Instead of absorbing the evolved H,S in alkaline lead-nitrate 
solution, a solution of 8 g. of cadmium chloride in 250 cc. of 
water and 150 cc. of NH,OH (sp. gr. 0.90) may be used. The 
CdS precipitate may be filtered on a weighed Gooch, washed 
with water containing a little NH,OH, dried at 100° C., and 
weighed. Calculate to ZnS. It is better to filter the CdS on a 
small filter and wash as above, then place filter and precipitate 
in a beaker and dissolve in HCl and KCIO, (keeping at room 
temperature at first), filter out any paper pulp or insoluble 
matter; make filtrate alkaline with NH,OH, then just acid with 
HCl, heat to boiling and precipate with BaCl, in usual manner. 
Filter, wash, ignite, and weigh BaSO,. Calculate to ZnS. 

For very rapid work the contents of the absorption flask, 
after all H,S has been absorbed, may be washed into a vessel 
with cold water and diluted to about one liter, acidified with 
concentrated HCl and titrated with standard iodine solution, 
using starch indicator. (The precipitate should be completely 
dissolved.) The iodine solution is prepared by dissolving about 
12.7 g. of pure resublimed iodine and 18 g. of KI in a little water 
and then diluting to one liter. 


ANALYSIS OF WHITE PAINT PIGMENTS 323 


While the above methods have proved generally satisfactory, 
the evolution method for zine sulfide is rather tedious. Breyer 
and Croll of the N. J. Zinc Co. omit this method and secure the 
zine sulfide content by difference, after determining total zinc 
and barium sulfate. Their methods for the latter as communi- 
cated recently to the writer, are given below: 

Total Zine in Lithopone (B * C Method).—A 2 gram sample 
is weighed out into a 150 ce. beaker and treated with 25 cc. con- 
centrated hydrochloric acid. When action has largely ceased, 
80 ce. of 1:1 sulphuric acid is added, evaporated to fumes and 
the heating continued, with beaker covered, until all barium 
sulphate has gone into solution. After cooling, cold water is 
poured in to nearly fill the beaker. The solution and reprecipi- 
tated barium sulphate are then poured into a graduated 500 cc. 
flask, water added to the mark and the whole thoroughly mixed 
and filtered. A 250 cc. portion of the clear filtrate is measured 
out into a 600 cc. beaker, 20 cc. of citric acid solution and 10 ec. 
of ferric nitrate solution added. The excess acid is neutralized 
with ammonia, using litmus paper, and a definite excess of 15 cc. 
of ammonia added. 

The solution is brought to a boil and then the titrating solu- 
tion of potassium ferrocyanide is run in with constant stirring 
until within 1 cc. of the end point. The addition is continued 
0.2 cc. at a time until all the zinc has been precipitated as indi- 
cated by a blue coloration appearing when a drop of the solu- 
tion is added to a few drops of acetic acid on a test plate. 

The potassium ferrocyanide solution is standardized by start- 
ing with a weighed amount of C.P. zinc approximately equal to 
the amount to be titrated in the sample, and carrying through 
the same procedure. 

Barium Sulphate in Lithopone (BX C Method).—A 1 gram 
Sample is weighed out into a platinum crucible, mixed with 6-8 
grams of sodium carbonate and fused for twenty minutes over 
a Bunsen Burner and twenty minutes over a blast lamp. The 
fusion is then leached out with about 200 cc. of hot water in a 
250-cc. beaker. The insoluble barium carbonate is filtered off 
and washed thoroughly with hot sodium carbonate solution (2 
grams per liter). The barium carbonate is then dissolved from 
the paper into a 600-cc. beaker with hot 1:4 hydrochloric acid, 


324 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


washing thoroughly. The solution is diluted to about 400 cc. 
neutralized with ammonia and then made slightly acid with 
hydrochloric acid (2 cc. excess). The solution is heated to boil- 
ing and barium sulphate precipitated with hot ammonium sul- 
phate solution (40 grams per liter). After standing four hours © 
on a steam plate, the barium sulphate is filtered off on to a 
weighed, ignited Gooch crucible. See also Interdepartmental 
Specification in back of volume. . 

For a scheme of analysis for Cadmium Lithopone see chapter 
on Yellow Pigments, page 359. 


ANALYSIS OF DRY TITANOX 


The recent advent of titanium oxide as a constituent of white 
paints should be of interest to analytical chemists, since special 
methods are necessary for the determination of the titanium 
present. There is given below L. E. Barton’s method for the 
analysis of dry titanium oxide pigment such as is made in the 
United States and which usually contains 75% barium sulphate 
and 25% titanium oxide. There is also given a method for the 
separation of zinc and lead from mixtures containing titanium. 

Determination of Barium Sulphate—Weigh 14 gram sample 
into 250 cc. Pyrex glass beaker; add 20 cc. concentrated sul- 
phuric acid and 7 or 8 grams sodium sulphate. Mix well and 
heat on hot plate until fumes of sulphuric anhydride are evolved 
and then heat directly over flame to boiling for five minutes or 
until solution is complete. Traces of silica, if any, remain as 
an insoluble residue. 

Cool, take up with 100 ce. of water, boil and filter off barium 
sulphate and silica, washing with 5 per cent sulphuric acid to 
free residue from titanium. 

Determination of Titaniwm.—The volumetric method used 
for determination of titanium is essentially that described by 
P. W. & E. B. Shimer (Proc. Eight Internat. Congress of Ap- 
plied Chem.) ; the method hereafter described differing prin- 
cipally in the form of reductor and also in a few details of oper- 
ation. 

Reagents.—Standard ferric ammonium sulphate solution. 
Dissolve 30 grams of ferric ammonium sulphate in 300 cc. 
water acidified with 10 cc. of sulphuric acid; add potassium per- 
manganate drop by drop as long as the pink color disappears, to 


ANALYSIS OF WHITE PAINT PIGMENTS WAS 


oxidize any ferrous to ferric iron; finally dilute the solution to 
one liter. 

Standardize this solution in terms of iron. The iron value 
multiplied by 1.4829 gives the value in titanic oxide (TiO,) ; and 
iron value multiplied by .86046 gives the value of the solution 
in terms of metallic titanium. 

Indicator—Saturated solution of potassium thiocyanate. 

Reductor.—As a reductor a 500 cc. dispensing burette is used. 
The internal dimensions of the burette are 15% inches by 22 
inches. 

The reductor is charged with 1200 grams of 20 mesh amal- 
gamated zinc, making a column about 12 inches high and hav- 
ing an interstice volume of about 135 cc. This form of reductor 
is convenient, and when used as hereafter described is adapted 
to maintaining hot solutions, which is essential for complete 
reduction of the titanium. 

The reductor is connected to a liter flask for receiving the 
reduced titanium solution through a three-hole rubber stopper, 
which carries also an inlet tube for carbon dioxide supply and 
an outlet tube for connecting with the suction pump. 

The reductor is prepared for use by first passing through it 
a little hot dilute sulphuric acid followed by hot water, finally 
leaving sufficient hot water in the reductor to fill to the upper 
level of the zinc. 

The hot filtrate from the barium sulphate determination is 
now introduced; about 10 cc. of water being drawn from the 
reductor into the original beaker to bring the solution to about 
the upper level of the zinc. The water thus removed will not 
contain any titanium if the operation has been conducted as 
described, but it serves as a safeguard and is also convenient 
to acidify this water with 10cc. sulphuric acid and reserve it on 
the hot plate to be used as an acid wash after the reduction of 
the sample solution. 

- The titanium solution is allowed to remain in the reductor for 
10 minutes. 

While the solution is being reduced, the receiving flask is con- 
nected to the reductor and the air completely displaced by carbon 
dioxide, conveniently drawn from a cylinder of the liquified 
gas. | 


\ 


~ 326 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


When the reduction is complete the receiving flask is con- 
nected with the suction pump, and while still continuing the 
flow of carbon dioxide the reduced solution is drawn out, fol- 
lowed by the reserved acid wash and then three or four 100 ce. 
washes with hot water. The displacement of the sample solu- 
tion and washing of the zinc is so regulated by means of the 
stopcock that the reductor is always filled with solution or water 
to the upper level of the zinc. 

When the washing is complete, gradually release the suction 
to prevent air being drawn back into the receiving flask. 

Disconnect the flask, add 5 cc. of potassium thiocyanate solu- 
tion as indicator and titrate immediately with standard ferric 
ammonium sulphate solution, adding the solution rapidly until a 
brownish color is produced, which will remain for at least one 
minute. 

ANALYSIS OF PAINTS CONTAINING TIO, 

After the pigment has been extracted and dried, a sample is 
weighed out and decomposed by the ordinary acid treatment. 
Weigh 1 gram into a 250 cc. Pyrex beaker; add 40 cc. concen- 
trated sulphuric acid and 15 grams ammonium sulphate. Mix 
well and heat on a hot plate until fumes of SO, are evolved, and 
then continue heat to boiling for five minutes. Silica, if pres- 
ent, will, of course, remain undissolved. Cool, take up with 200 
ce. water, boil and filter off lead sulphate, barium sulphate, 
silica, and similar acid insoluble inert pigments. Separate as 
usual. (See above.) The filtrates should contain the titanium 
and zinc in solution as sulphates. 

To the filtrate ammonia is added in excess, which precipitates 
the titanium with the iron group. For the complete separation 
of zinc from the iron group, the hydroxide precipitate should be 
re-dissolved in acid and a second precipitation with ammonia 
should be made.. Zine may then be determined in the combined 
filtrate. 

Titanium should be determined on a separate sample, as de- 
scribed in the above method for dry TiO, pigments. 

See also F. S. B. Spec. No. 115, back portion of this volume and 
new specification of Federal Specification Board to be issued in 
February, 1925, on Titanox-Zinc Ready Mixed Paint Resistant 
to Sulphur Gases. 


ANALYSIS OF WHITE PAINT PIGMENTS 327 


ANTIMONY OXIDE PIGMENTS 


Antimony Oxide.*};—Antimony trioxide (Sb,O,) a fume pig- 
ment that has recently been introduced, may be occasionally 
found in certain classes of mixed paints. After being brought 
into solution, it may be quantitatively estimated by oxidation 
with permanganate or iodine. (See pages 27 and 28, Scott’s 
Standard Methods of Chemical Analysis.) 


SILICA OR SILEX—-CHINA CLAY—ASBESTINE 


These pigments, while all true silica pigments, are widely 
different from the standpoint of physical structure. A micro- 
scopic examination is of great value, showing silica or silex to 
consist of small, sharp particles, china clay to be tabloid in ap- 
pearance and asbestine to consist of long, rod-like fibrous par- 
ticles. 

Moisture—Heat 2 grams at 105° for two hours. 

Loss on Ignition.—Ignite 1 gram to constant weight in a 
platinum crucible. 

Insoluble Matter.—Boil 2 grams for thiry minutes with 50 
ec. HCl (1:1), add 50 cc. of water, wash, ignite, and weigh in- 
soluble residue. 

In the case of china clay, or asbestine, a sodium carbonate 
fusion should be resorted to, with the subsequent dehydration of 
the silica. 

The insoluble residue in either case is volatilized with H,SO, 
and HF in the usual manner, any loss in weight being considered 
silica. Any residue is fused with sodium carbonate, the fusion 
being added to the original filtrate. Should BaSO, be present, 
the melt is digested with warm water, the BaCO, filtered off, 
washed, dissolved in hot diluate HCl and precipitated and de- 
termined as BaSQ,. 

The filtrates, combined from the preceding filtrations, are ex- 
amined for alumina, iron, manganese, calcium and magnesium 
in the usual way. 

Should it be necessary to determine the alkalies present, a 


* See “The evaluation of white pigments with special reference to anti- 
mony oxide,” by H. E. Clarke, J. Oil & Colour Chemists’ Assoc., Vol. 4, 
pp. 2-26 (1921); Chem. Abstrs., Vol. 15, p. 2197 (1921). 

+ See also Circulars 152 and 153 of Scientific Section for results of ex- 
posure tests. 


328 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


separate sample is treated according to the J. Lawrence Smith 
method as described in Bulletin No. 700, U. S. Geological Survey. 

Carbon Dioxide-—Determine by evolution with HCl, weighing 
in soda-lime, KOH solution, or by absorbing in Ba(OH), solu- 
tion and titrating or weighing as BaCO,. 

Any excess of calcium is reported as oxide. The magnesium 
is calculated as MgO, unless the carbon dioxide is in excess of 
the amount of calcium present, in which case it is reported as 
MgCoO,, and the remainder as MgO. 


CALCIUM PIGMENTS 
WHITING, PARIS WHITE, SPANISH WHITE, AND CHALK 


These pigments are of the following composition: 

Whiting.—The natural form of calcium carbonate. 

Paris White.—The artificial form of calcium carbonate. 

Gypsum.—The hydrated form of calcium sulphate, of formula 
CasO 7. 2H-0; 

These pigments are analyzed in the following manner: 

Moisture.—Heat 2 grams at 105° C. for two hours. 

Total Soluble Lime.*—Weigh out 0.75 g. of the pigment into 
a small crucible, ignite cautiously to dull redness to destroy 
organic matter, cool, transfer to a 400-ce. beaker, add 20 ce. of 
HO, cover, then add 15 cc. of concetrated HCl and 3 or 4 drops 
of concentrated HNO,, and boil till all the soluble matter is dis- 
solved and all the CO, expelled. Wash off and remove the 
cover, dilute to about 150 cc. with freshly boiled H,O, heat to 
boiling and add dilute NH,OH (sp. gr. 0.96) carefully until a 
shght permanent precipitate forms. Heat to boiling and add 10 
cc. of a 10-per-cent solution of oxalic acid; stir until the oxides 
of iron and aluminum are entirely dissolved and only a slight 
precipitate of calcium oxalate remains. Now add 200 cc. of 
boiling H,O and sufficient saturated solution of ammonium 
oxalate (20 to 25 cc.) to precipitate the lime. Boil and stir for 
a few moments, remove from the heat, let settle and filter on an 
11-cm. filter. Wash 10 times with 10-to-15-cc. portions of hot 
water. Place beaker in which precipitation was made under the 
funnel, pierce apex of filter with stirring rod and wash pre- 


* Meade, ‘Portland Cement.” 


ANALYSIS OF WHITE PAINT PIGMENTS 329 


cipitate into beaker with hot water, pour warm dilute H,SO, 
(1:4) through paper and wash a few times; add about 30 cc. of 
the dilute H,SO, (1:4), dilute to about 250 cc., heat to 90° C. 
and titrate at once with standard KMnO, solution (solution 
should not be below 60° C. when end-point is reached). The 
KMn0O, is best standardized against Bureau of Standards sod- 
ium oxalate.* Calculate to CaO and CaCO.,,. 

Mixed Calcium and Magnesium Carbonates.t—Weigh 1 g. of 
the finely powdered sample into a small porcelain dish, add 25 
ec. of normal HCl, cover with a watch glass, and when efferves- 
cence has ceased, heat to boiling. Cool and titrate with normal 
NaOH solution, using methyl orange as indicator. 

The calculation is as follows: 

One gram CaO=35.7 cc. of normal acid. CaO x 1.7844 = 
CaCO,. Subtract number of cubic centimeters of NaOH re- 
quired from 25; result gives number of cubic centimeters of nor- 
mal acid corresponding to the CaCO, + MgCO,. Multiply the 
weight of CaO in 1 g. of sample (as found in preceding section 
on total soluble lime) by 35.7; product gives number of cubic 
centimeters of normal acid corresponding to the CaO present; 
subtract from total number of cubic centimeters of acid re- 
quired by CaCO, + MgCO, and multiply result by 0.042, obtain- 
ing weight of MgCO, in 1 g. of sample. The MgCO, determined 
by this process should not differ more than 0.25 per cent from 
that obtained by more elaborate methods. It is to be noted that 
this method is a measure of the total alkalinity, and if Ca or Mg 
are present in other forms than carbonate, a complete analysis 
would be necessary to give percentages of CaCO, and MgCO,. 


BARYTES AND BLANC FIXE 


Of these two barium pigments used in the manufacture of 
paints, barytes is the natural barium sulphate, while blanc fixe 
is precipitated barium sulphate. 

The following method may be used for the analysis of these 
pigments: 

Moisture.—Heat 2 grams at 105° C. for two hours. 

Loss on Ignition—lIgnite 1 gram to constant weight. The 


* Circular No. 40, Bureau of Standards. 
+ J. W. Mellor, “A Treatise on Quantitative Inorganic Analysis,” p. 522. 


330 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


loss will be reported as loss on ignition, and will consist of free 
and uncombined water, carbon dioxide and organic matter. 

Barium Sulphate.—Boil 1 gram with dilute HCl, evaporate to 
dryness, moisten with HCl, add water, boil, filter and wash. 
Should lead be present in the insoluble residue, as shown by the 
action of H,S, treat the insoluble residue with a little (1:1) 
HCl and several drops of H,SO,. Filter, wash and weigh the 
residue. Treat the ignited residue with H.SO, and HF, evap- 
orate to dryness and ignite. The residue should show no loss as 
silica. The filtrate is examined for alumina, iron, calcium and 
magnesium in the usual manner. 

Soluble Sulphates.—Treat 1 gram with 20 ce. cone. HCl, dilute 
to 200 cc. with hot water, boil, filter, wash, add NH,OH until 
neutral, make acid with HCl and precipitate any sulphat as 
BaSO,. Determine in the usual manner. Calculate to CaSO,. 
If carbonates are present, calculate the remaining CaO to 
CaCO,. Any excess of oxide is reported as CaO. 

Carbon Dioxide.—Determine as outlined under silica. If any 
barium carbonate is present, it is determined in the filtrate 
from the preliminary HCl treatment, by precipitation and 
weighing, as BaSO,. Any excess of carbon dioxide over the 
barium is reported as calcium carbonate. 


ANALYSIS OF A COMPOSITE WHITE PAINT 


A white paint may consist of a mixture of any of the preced- 
ing pigments, except that lead pigments and lithopone are sel- 
dom found together. 

After separation from the oil and other liquids as outlined 
in Chapter XXIV, page 213, the white pigment mixture may be 
rapidly analyzed by the following method. It is, however, often 
advisable to resort to a qualitative examination before beginning 
the quantitative analysis. Also note method of analysis in inter- 
departmental specifications. 

Insoluble Residue.—Boil 1 gram of the sample with 20 cc. 
(1:1) HCl. Evaporate to dryness, moisten the residue with a 
few cc. of concentrated HCl, allow to stand a few minutes, dilute 
with hot water, boil, filter and wash the insoluble residue thor- 
oughly with hot water. Treat the insoluble residue with (1:1) 
HCl and 2 cc. H,SO, to remove the last traces of lead. Filter, 


ANALYSIS OF WHITE PAINT PIGMENTS dol 


wash and weigh the insoluble residue. Determine the silica by 
volatilization with H,SO, and HF. Any loss is reported as silica. 
Determine the BaSO, in the residue by boiling with dilute HCl 
or making a potassium bisulphate fusion. The residue remain- 
ing after either of these treatments is reported as barium sul- 
phate. 

Total Lead.—This constituent can be best determined on a 
separate sample. To 1 gram add 10 cc. of conc. HNO., boil, add, 
after cooling, conc. H,SO, and evaporate to strong SO, fumes. 
Dilute with water, allow to stand several hours, filter, wash 
slightly, dissolve and determine the lead volumetrically as out- 
lined under Basic Sulphate White Lead. 

Lead can also be determined in the combined filtrates from 
the insoluble residue. Precipitate the lead in an acid solution 
with H,S and determine volumetrically in the above outlined 
manner. 

To determine whether both sublimed white lead and corroded 
white lead are present, treat a separate portion of the paint with 
boiling acetic acid, filter and collect the insoluble residue. De- 
termine the lead either in the filtrate or in the insoluble residue 
by the volumetric method. The lead soluble in acetic acid is the 
basic carbonate of lead and the lead oxide from the sublimed 
white lead, while the lead sulphate from the sublimed white lead 
remains insoluble. 

Alumina and Iron Oxide—Remove the H,.S from the filtrate 
by boiling, after removal of the lead, and precipitate the 
hydroxides in an ammoniacal solution after boiling with the ad- 
dition of a few drops of HNO,. Determine and separate in the 
usual manner. 

Zinc.—Precipitate the zinc in the filtrate from the alumina 
and iron precipitation, after acidifying with acetic acid, and de- 
termine the zinc as outlined under Basic Sulphate White Lead. 

Calcium and Magnesium.—Determine the calcium and mag- 
nesium in the filtrate from the precipitation of zinc sulphide in 
the usual manner, testing, however, first for the presence of 
barium. 

Sulphate.—Determine as outlined under Zinc Lead and 
Leaded Zincs. 


332 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Sulphide.—Should lithopone be present, separate the zinc 
oxide and zinc sulphide as outlined under Lithopone. 

Carbon Dioxide.—Determine as outlined under Silica. 

Calculations.—Silica is reported as silica, except where alu- 
mina is present, showing the presence of china clay. In this 
case, calculate the alumina to clay by the method of Scott. — 

Weight of Al,O, + 2.5372 — weight of clay. 

Weight of clay < 0.4667 = weight of SiO, in clay. 

Any difference greater than 5% may be considered silica. 

Barium sulphate is reported as barium sulphate or as lith- 
opone, if zine sulphide is present, according to the given com- 
position of lithopone, 70% barium sulphate and 30% zine sul- 
phide. 3 

Lead is reported as Basic Carbonate of Lead on the formula 
2PbCo,.Pb(OH).. 

Calculate lead soluble in acetic acid, after determining CO,, 
to basic lead carbonate and any residual lead to lead oxide which, 
together with the lead sulphate, is reported as Sublimed White 
Lead. 

Should calcium sulphate be present the portion soluble in 
water is examined for lime or sulphuric acid and calculated to 
calcium sulphate, any residual lime being calculated to calcium 
carbonate and any residual sulphuric acid being calculated to 
lead sulphate. Any residual CO, after calculating calcium car- 
bonate is calculated to white lead and any residual lead is cal- 
culated to lead oxide. 

Lead oxide should not be reported except in the presence of 
lead sulphate. Any large percentage of magnesium denotes the 
presence of asbestine. 


See also Interdepartmental Specifications in back of volume. 


a a? oe ‘a: = ‘2 foNGy Fie ‘ef = fle 


De Oe eek. eS 


CHAPTER XXXVI. 


ANALYSIS OF LEAD OXIDES 


These pigments in the pure form are oxides of lead, of the 
generally accepted formula, Pb,O,, being probably mixtures of 
lead monoxide, and lead dioxide. In chemical composition they 
are the same, the proportions of lead monoxide and lead dioxide 
varying, however, but by their physical structure and color they 
can be readily differentiated. 

Two methods are given for the analysis of this pigment. 

Moisture.—Dry 2 grams at 105° for two hours. 

Organic Color.—Boil 2 grams with 25 cc. of 95% ethyl alcohol, 
let settle, decant off the supernatant liquid; boil residue with 
water, decant as before and boil residue with very dilute 
NH,OH. If either the alcohol, water or NH,OH is colored, 
organic coloring matter is indicated. 

Total Lead and Insoluble Residue.—Treat 1 gram with 15 ce. 
of HNO, (1:1) and sufficient hydrogen dioxide to dissolve all 
the PbO, on warming. If any insoluble matter is present, add 
25 ec. of water, boil, filter and wash with hot water. Insoluble 
contains free SiO,, and should be examined for BaSO, and 
silicates, if appreciable. To the original solution or filtrate 
from insoluble, add 20 cc. of conc. H,SO, and evaporate to SO, 
fumes; cool and determine lead as lead sulphate either gravi- 
metrically or volumetrically. If the sample contains soluble 
barium salts, the PbSO, will contain BaSO, and should be 
treated with acid-ammonium acetate solution, the lead being de- 
termined in the filtrate. 

Determination of Lead Peroxide (PbO,) and True Red Lead 
(Pb.0,). (Method of Diehl,* modified by Topft—not applic- 
able when substances are present, other than oxides of lead, 
that liberate iodine under conditions given.) 

Weigh 1 gram of finely ground sample into a 200-cc. Erlen- 
meyer flask, add a few drops of distilled water and rub the 
mixture to a smooth paste with a glass rod flattened on end. 
Mix in a small beaker 30 grams of C.P. “Tested Purity” crystal- 


*Dingl. Polyt. Jour., 246, 196. 
+ Zeitschrift fiir analytische Chemie, 26, 296. 


333 


334 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


lized sodium acetate, 2.4 grams of C.P. potassium iodide, 10 cc. 
of water and 10 cc. of 50% acetic acid; stir until all is liquid, 
warming gently; if necessary add 2 or 3 cc. of H,0, cool to room 
temperature and pour into the flask containing the red lead. 
Rub wit hthe glass rod until nearly all the red lead has been 
dissolved; add 30 cc. of water containing 5 or 6 grams of sodium 
acetate, and titrate at once with decinormal sodium thiosulphate, 
adding the latter rather slowly and keeping the liquid constantly 
-In motion by whirling the flask. When the solution has become 
light yellow, rub any undissolved particles up with the rod until 
free iodine no longer forms, wash off rod, add the sodium 
thiosulphate solution until pale yellow, add starch solution and 
titrate until colorless, add decinormal iodine solution until blue 
color is just restored and subtract the amount used from the 
volume of thiosulphate that had been added. : 

Calculation.—The iodirie value of the sodium thiosulphate 
solution multiplied by 0.94193 = PbO,; the iodine value multi- 
plied by 2.69973 = Pb,O,; the PbO, value multiplied by 2.86616 
= POO r: . 

Sodium Thiosulphate Solution (decinormal) —Dissolve 24.83 
grams of C.P. sodium thiosulphate, freshly pulverized and dried 
between filter paper, and dilute with water to 1 liter at a tem- 
perature at which the titrations are to be made. The solution 
should be made with well-boiled H,O, free from CO., or let stand 
eight to fourteen days before standardizing. Standardize with 
pure, resublimed iodine and also against pure potassium iodate. 
The two methods of standardization should agree within 0.1% on 
iodine value. In place of pure iodine, a decinormal solution of 
potassium permanganate may be used for standardization. 

Starch Solution.—Two to 3 grams of potato starch are stirred 
up with 100 cc. of 1% salicylie acid solution, and the mixture 
boiled till the starch is practically dissolved and then diluted to 
1 liter. | 

The second method for determination of the lead peroxide or 
true red lead content is somewhat shorter. 

Treat 1 gram in a beaker with 15 cc. of nitric acid, sp. gr. 1.2 
(110 ce. nitric acid sp. gr. 1.42 to 100 ce. of water). Stir the 
sample until all trace of red color has disappeared. Add from 


ANALYSIS OF LEAD OXIDES Soper 


a calibrated pipette or burette exactly 10 cc. of dilute hydrogen 
dioxide (1 part of 3% hydrogen dioxide to 3.5 parts of water). 
Add about 50 cc. of hot water and stir until all the lead dioxide 
has passed into solution. In the case of some coarsely ground 
oxides the contents of the beaker may have to be gently heated 
to effect complete solution. After the oxide has completely 
passed into solution, dilute with hot water to about 250 cc. vol- 
ume and titrate directly with a standard potassium perman- 
ganate solution, having an iron value of 0.005. Titrate to the 
faint pink permanganate color. A blank titration on the hydro- 
gen dioxide solution must now be made. 

Into a beaker pour 15 cc. of nitric acid of above strength and 
add exactly the same amount of hydrogen dioxide (10 cc.). 
Dilute to 250 cc. with hot water and titrate with standard potas- 
sium permanganate solution to a faint pink color. 

The difference between the number of cc. of potassium per- 
manganate required for the blank titration and the number re- 
quired for the red lead titration is the amount required for the 
hydrogen dioxide which was reacted on by the red lead. The 
difference between the two amounts of potassium permanganate 
required multiplied by 3.058 grams gives the percentage of red 
lead present. The difference multiplied by 1.067 gives the per- 
centage of PbO, present. 

Lead in Extracted Pigment.—Another very good method of 
determining the percentage of true red lead in an extracted pig- 
ment is to weigh the sample into a flask, add no water, but sub- 
stitute 10 cc. of a mixture of 7 parts of chloroform and 3 parts 
of glacial acetic acid, and proceed in the usual manner as out- 
lined above. 


——_—_— 


The latest methods for the examination of red lead and lith- 
arge, together with colorimetric measurements for the de- 
termination of copper and iron in pig lead, lead oxides, and lead 
carbonate, as furnished the writer by Dr. John A. Schaeffer, J. 
A. Calbeck and B. S. White, of The Eagle-Picher Lead Co., are 
given herewith. 


336 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


A COLORIMETRIC METHOD FOR THE DETERMINATION OF COPPER 
AND IRON IN PIG LEAD, LEAD OXIDES, AND LEAD 
CARBONATE* 


Most methods in use for the determination of the small per- 
centage of copper contained in pig lead, lead oxides and lead 
carbonate are long and tedious. This is especially true in those 
instances where refined metal serves as the base for the finished 
product and the copper content being extremely low, many diffi- 
culties present themselves; these can be overcome by the use of 
this colorimetric method. 

While the estimation of the iron content in these compounds 
can be readily carried out colorimetrically by a Separate ana- 
lysis,t it has been found that the following method, which com- 
bines the determination of both copper and iron colorimetrically 
In one analysis, adds greatly to the rapidity and accuracy in 
finding the percentages of these impurities. The method not 
only eliminates the use of hydrogen sulphide, but it shortens 
the time of a single analysis to 30 to 40 minutes, while the re- 
sults attain the same degree of accuracy as those established by 
the longer and more complicated methods. 

The method of procedure varies somewhat with the nature 
of the sample to be examined: hence, it will be necessary to 
make especial mention of red lead. | 


ANALYSIS OF Pic LEAD, LITHARGE AND LEAD CARBONATE 
FOR COPPER 

Weight of Sample.—In analyzing refined pig lead, or lead 
compounds made from refined metals, it is necessary, owing to 
the small percentages of copper and iron usually present, to use 
large samples. It has been found, by the use of this method, 
that smaller samples may be used with equally accurate results, 
thereby reducing the bulk to be handled and eliminating any 
errors which frequently result from the use of large volumes. 
A sample weighing 30 grams has been found sufficiently large 
for refined products, and not over 10 grams need be used for the 
crude or unrefined material. 

Method of Procedure.—Weigh the finely divided sample into 
a 400-cc. beaker, and add small portions of hot (1:1) nitric 
acid until solution is effected. If any basic lead nitrate has been 


* J. Ind. Eng. Chem., 7, 1035 (1915). 
+J. Ind. Eng. Chem., 4, 659 (1912). 


ANALYSIS OF LEAD OXIDES 337 


formed, dilute slightly with warm water and boil. Add 32 cc. 
(1:1) sulphuric acid, stirring constantly while adding. Let the 
precipitate settle, and decant filtrate through a coarse filter 
paper. Wash four times by decantation, using small portions 
of warm, distilled water. Transfer the precipitate to the paper, 
wash again and allow to drain. Make the filtrate neutral with 
ammonium hydroxide and add 4 cc. excess. Boil for a short 
time and filter. Wash the precipitate well with warm water, 
and reserve for the determination of the iron. MRender the 
filtrate acid with special c. p. hydrochloric acid, adding not more 
than two drops excess. Add six drops of (1:10) potassium 
ferrocyanide solution, filter through close filter papers using 
two to each funnel. Catch the filtrate and inspect for copper 
ferrocyanide. Let the precipitate drain well without washing. 
Dissolve the copper ferrocyanide off of the paper with alternate 
washings of small portions of ammonium hydroxide and hot 
water. Wash well and keep the bulk to 30 or 40 cc. Render ! 
slightly acid with hydrochloric acid, adding not over two drops 
excess. Transfer to a 100-cc. Nessler tube, and dilute to mark 
with distilled water. The copper is then determined colori- 
metrically according to a modification of the method of Car- 
nelly.* 

In another Nessler tube, place 10 cc. of 5 per cent ammonium 
nitrate solution, two drops concentrated nitric acid and 90 cc. 
distilled water, add from a burette graduated to tenths of 1 cc., 
standard copper sulphate solution until the color matches the 
sample under examination. 

Standard Copper Sulphate Solution.t—“Dissolve 0.393 gram 
of pure CuSO,.5H,O, in one liter of distilled water. 1 cc. = 
0.0001 gram of copper,” or 0.00033 per cent when using a 30- 
gram sample. — 

Analysis of Red Lead for Copper.—Treat 30 grams of the 
sample with 40 ec. (1:1) nitric acid, using great care that the 
violence of the reaction does not cause the sample to froth over 
the beaker. Slowly add 30 to 40 cc. of 8 per cent hydrogen 
peroxide, stirring constantly. Boil until solution is effected, and 
proceed as directed above. 

Sodium sulphite c. p. may be used in place of the hydrogen 


* Sutton’s Volumetric Analysis, p. 204. 
+ Sutton’s Volumetric Analysis, p. 205. 


358 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


peroxide for effecting the solution of lead peroxide, adding it 
dry in small portions and boiling until no brown lead peroxide 
is present. 

Determination of Iron in the Above Compounds.—For the 
iron determination, use the precipitate of iron hydroxide re- 
moved from the copper solution, proceeding as follows: Dis- 
solve the precipitate contained on the paper with (1:1) hydro- 
chloric acid, collecting the filtrate in a 300-cce. volumetric flask. 
Wash the paper free from acid with hot, distilled water, dilute 
to mark, and mix thoroughly. Place 10 ec. in a 100-ceec. Nessler 
tube, add three drops nitric acid, 10 ee. (1:15) ammonium sul- 
phocyanide solution, dilute to mark and compare with a stand- 
ard iron solution.t 

The color is compared with a blank made in the following 
manner: A solution of ferric ammonium sulphate of known 
strength is required. This is made by dissolving 0.7022 gram 
of ferrous ammonium sulphate in water. Acidify with sul- 
phuric acid, heat to boiling and add a solution of potassium 
permanganate until all the iron is converted to the ferric condi- 
tion. Only the very slightest pink tinge may be present after 
the addition of the potassium permanganate, as this tinge will 
fade away, while the presence of a pink color tends to vitiate 
the results. Allow the solution to cool and dilute to one liter. 
One cc. of this solution equals 0.0001 gram of iron. 

Prepare the blank by pouring into a 100-cc. Nessler cylinder, 
10 cc. ammonium sulphocyanide solution, and three drops of 
concentrated nitric acid. Dilute to 100 ec. and titrate to the 
exact color developed in the sample under examination, by the 
addition of the standard ferric ammonium sulphate solution. 
One cc. of this solution equals 0.01 per cent iron as the 10 cc. 
removed from the flask contained 1 gram sample. It will be 
found that the color can be accurately compared to within 0.001 
per cent of iron content. 

Comparison of Results on Copper.—Table XLVIII shows the 
results obtained by the above method, as compared with the 
method set forth by Fresenius,* on two sets of samples and a 
copper sulphate solution of known strength. 


{£J. Ind. & Eng. Chem., 4 (1912), 659. 
* Fresenius’ Quantitative Chemical Analysis, Vol. II, p. 584. 


ANALYSIS OF LEAD OXIDES 339 


Precautions and Interfering Elements.—I£ the sample con- 
tains much zinc, the following method may be used for remov- 
ing it: The filtrate from the iron precipitation, before precipi- 
tating the copper ferrocyanide, is rendered slightly acid with 
acetic acid, and 5 cc. of an 8 per cent sodium ammonium phos- 
phate solution are added; boil, cool, filter and treat the filtrate as 
before outlined. 


TABLE XLVIII—Comparative Results (Percentages Cu) by Method of 
Fresenius and of Author 


Litharge and 
Pig Lead Red Lead CuSO, Solution 
No. 
Fres. Color. Fres. Color. Fres. Color. Lee 
present 
1 0.0009 | 0.00088 | 0.002 0.002 0.002 0.002 0.002 
2 0.0013 | 0.0013 | 0.0008 | 0.0008 | 0.0008 | 0.0008 | 0.0008 
3 0.0009 | 0.00088 | 0.0009 | 0.00088 | 0.00066 | 0.00066 | 0.0007 
4 0.002 0.002 0.0007 | 0.0007 | 0.001 0.001 0.001 
5 0.001 0.001 0.0015 | 0.0015 | 0.00066 | 0.00066 | 0.00066 
6 C200 loa 0015, > 6.00388. | 0.0038 | 0.0015. | 0.0015 | 0.0015 
cf 0.0012 | 0.0012 | 0.00088 | 0.00088 | 0.00088 | 0.00088 | 0.00088 
8 0.0079 | 0.0079 | 0.00088 | 0.0009 | 0.0009 | 0.00088 | 0.0009 | 
9 eu tawoeo O0lo: | 6:0013 }.0:0018) |) 0.0015. }.0.0015° | 0.0015 
10 0.0004 | 0.0004 | 0.00066 | 0.00066 | 0.0007 | 0.00066 | 0.0007 


Lead, when present in not too large quantity, has little or no 
effect on the accuracy of the colorimetric comparison of copper. 
If a faint white cloud of lead ferrocyanide should develop in the 
sample under examination, the addition of a small amount of 
very dilute lead nitrate solution to the standard will overcome 
this difficulty. 

Reagents and Indicators.—This method presupposes the use 
of absolutely pure reagents, especially free from iron and cop- 
per. Use litmus paper as an indicator, as all other indicators, 
once introduced, will affect the final color. 


RED LEAD AND ORANGE MINERAL 


Schaeffer’s Latest Method * 
Moisture.—Dry 2 grams of the sample for 2 hours at 105° C. 
The loss will be moisture. 


* See Chemical Analysis of Lead and Its Compounds. Schaeffer, White 
and Calbeck. Pub. by The Eagle-Picher Lead Co., Joplin, Mo. 


340 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Red Lead, or Lead Dioxide.t—Treat 1 gram of the sample 
in a beaker with 15 cc. of nitric acid, specific gravity 1.2 (110 
ec. nitric acid, specific gravity 1.42, to 100 cc. of water. This 
solution should be aerated to free it from all nitrous fumes). 

Stir the sample until all trace of red color has disappeared. 
Add from a calibrated pipette or burette exactly 10 cc. of dilute 
hydrogen peroxide (1 part of 3-per-cent hydrogen peroxide to 
3.5 parts of water). Add about 50 cc. of hot water and stir 
until all the lead dioxide has passed into solution. In the case 
of some coarsely ground oxides the contents of the beaker may 
have to be gently heated to effect complete solution. After the 
oxide has completely passed into solution, dilute with hot water 
to about 250 cc. volume and titrate directly with a standard 
potassium permanganate solution, having an iron value of 0.005. 
Titrate to the faint pink permanganate color. A blank titration 
on the hydrogen peroxide solution must now be made. 

Titration of Hydrogen Peroxide, and Calculation of Results.— 
Into a beaker pour 15 cc. of nitric acid having the strength as 
above given and add exactly the same amount of hydrogen 
peroxide (10 cc.). Dilute to 250 cc. with hot water and titrate 
with standard potassium permanganate to a faint pink color. 

The difference between the number of cubic centimeters of 
potassium permanganate required for the blank titration and 
the number required for the red lead titration is the amount 
of potassium permanganate required for the hydrogen peroxide 
which was reacted on by the lead dioxide. The difference be- 
tween the two amounts of potassium permanganate required 
multiplied by 3.058 gives the percentage of red lead present 
according to the following proportion: 

Let X = % Pb,O, per cc. difference 
2 Fe:Pb,0, :: 0.005: X 
112:685 :: 0.005: X 
X equals 3.058 

To determine the lead dioxide present multiply this difference 
by 1.067 according to the following proportion: 

Let Y = % PbO, per ce. difference 
2 Fe:PbO, :: 0.005 : Y 
112 : 239 :: 0.005 - Y 
Y equals 1.067 


iJ. Ind. Eng. Chem., 8, 237 (1916). 


oye a, ee 


ANALYSIS OF LEAD OXIDES 341 


These calculations have been arrranged in a series So devised 
as to permit the direct’ reading of the red lead percentage. The 
basis of the calculations depends on the fact that each cc. of 
potassium permanganate solution (iron value, 0.005) is equiv- 
alent to 3.058 per cent of true red lead; or, each 0.1 cc. is 
equivalent to 0.3058 per cent true red lead on a one-gram sample. 

A red lead or orange mineral having 100-per-cent true red 
lead content requires 32.7 cc. potassium permanganate solution 
of the above strength. 

The calculation, therefore, arranges itself as follows: Each 
0.1 cc. on the selected burette represents 0.3058 per cent true 
red lead. The number 32.7 being equivalent to 100 per cent 
occupies an analogous position on the chart. 

Calculations should be continued upward to 40.0 or to that 
point where the hydrogen peroxide solution used is of such 
strength that 10 cc. of the hydrogen peroxide solution require 
40 ce. of the potassium permanganate solution. Calculations 
should be continued downward to 9.48 per cent true red lead 
content. 

In using the series the chart is attached to the burette by a 
serew clamp. The blank determination is first made on the 
hydrogen peroxide solution and the value found is placed op- 
posite zero on the burette. In the analysis of the red lead the 
value is then read off directly. As a hypothetical case we wili 
use a hydrogen peroxide solution with a blank titration of 34.1 
ec. In the analysis of a red lead or orange mineral 4.2 cc. of the 
potassium permanganate solution is required for a final titration 
value. The calculation shows the difference between the two 
readings to be 29.9 cc. or multiplied by 3.058 equals a true 
red lead percentage of 91.48 per cent. Comparing this with 
the series of calculations we find 4.2 cc. from the 34.1 to be 
91.43 per cent. 

Should it be preferred to determine the lead peroxide con- 
tent, the calculation will be based on the value 0.1067 for each 
0.1 ce. of the potassium permanganate solution. It is under- 
stood that the division must be made to correspond to the 0.1 
ec. divisions on the burette. 

It is always advisable to make several blank determinations 
each day when this analysis is constantly made and when only 


342 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


occasionally used a blank titration should be made before each — 


analysis. 


The strength of the hydrogen peroxide solution will vary but — 


the permanence of the permanganate solution renders the method 
accurate over a long period of time. 


Standard Potassium Permanganate.—It is necessary to al- — 


ways have a potassium permanganate solution with an iron 


value of exactly 0.005 if the method described for red lead is — 
used. Dissolve 5.75 grains c. p. salt in two liters distilled water — 


and store in a brown bottle in a dark place for a week or more. 


By this time all organic matter will have been oxidized and ~ 


after filtering the solution through an asbestos filter the solu- 


tion is ready for standardization. As small amounts of MnO, — 
destroy the permanence of this solution, it is necessary that it — 
be removed by filtering. The method described in Bureau of — 


Standards Circular No. 40 should be used. This method is as 


follows: 


In a 400-ce. beaker, 0.25 gram of sodium oxalate is dissolved — 
in 200 to 225 cc. of hot water (80-90° C.) and 10 ce. of (1:1) ~ 
sulphuric acid added. The solution is at once titrated with the — 
solution of permanganate, the solution being stirred continu- : 
cusly and vigorously. The permanganate must be added at the — 
rate of 10 to 15 cc. per minute and the last 0.5 to 1 ce. must be ~ 
added drop by drop, each drop being allowed to decolorize fully — 


before the next is added. The solution should not be below 


60° C. by the time the titration is completed. With a perman- : 
ganate solution having an iron value of 0.005 per cc., 41.66 cc. 


of the permanganate are required to react with 0.25 gram sod- 


ium oxalate. 

If the first titration shows that the solution is too strong a 
small amount of distilled water should be added. To calculate 
exactly how much water to add divide 41.66 by the number cc. 


required in the titration and multiply by the number of cc. re- 


maining in the bottle. The difference between this product and 
the number of cc. in the bottle will be the volume of water to add. 

If the solution is too weak this difference multiplied by 
0.00283 will be the grams of potassium permanganate salt to 
add. After the addition of water or salt the solution should 
again be titrated and if a titer of 41.66 is not obtained water or 


SO ee oa ee es 


i lita tain tg 


ANALYSIS OF LEAD OXIDES 343 


salt added until this titer is obtained. A solution carefully pre- 
pared in this manner should keep for months. 


ANALYSIS OF FLAKE RED LEAD 


SCHAEFFER METHOD 

In certain instances it is found that flake red lead is soluble 
only with the greatest difficulty by the above procedure. In 
cases where this difficulty is encountered the following method 
will be found to give excellent results: 

Digest 1 gram of the sample in a beaker with 15 cc. of nitric 
acid made up of a strength as given in the previous method. 
Boil the solution for a short time, add 10 cc. of a standard oxalic 
acid solution, the strength of which has been previously de- 
termined. Add 2 cc. of sulphuric acid (1:1). Boil the solu- 
tion and titrate with a standard solution of potassium perman- 
ganate having an iron value of 0.005. A blank titration on the 
same amount of oxalic acid must be made. The difference be- 
tween the amount of potassium permanganate required for the 
blank titration and that required for the red lead titration 
multiplied by the factor 3.058 or 1.067 will give the content of 
red lead or lead dioxide according to the proportions in the. 
previous analysis. 

Iron—The iron should be determined colorimetrically as 
described under Red Lead. 

Copper.—This constituent may be determined gravimet- 
rically, or colorimetrically. 

By the gravimetric method twenty grams of the sample are 
treated in a large beaker with 50 cc. nitric acid, 25 cc. of water 
and sufficient hydrogen peroxide to cause complete solution of 
the lead dioxide. 

Determine the copper as outlined under the Analysis of 
Litharge. 

The colorimetric method described under Red Lead is, how- 
ever, more rapid and convenient. 

Silica.—Silica is found to be present in oxides of lead both 
as free silica and as lead silicate, though usually in inappreciable 
amounts. 

Digest 2 grams of the sample in a casserole with 2 grams of 
potassium chlorate and 15 cc. of dilute nitric acid. Proceed 
from this point as outlined under the Analysis of Litharge. 


344 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Organic Color.—The adulteration of red lead and orange min- 


eral with organic coloring matter may be detected by adding | 


20 cc. of 95 per cent alcohol to 2 grams of the oxide, heating 


to boiling and allowing to settle. Pour off the supernatant 


liquid, boil with water, allow to settle and add a very small 


amount of ammonium hydroxide. If either the alcohol, water or | 


ammonium hydroxide are colored, it indicates organic coloring 
matter. The quantitative determination is exceedingly difficult 
and the organic color is usually estimated by difference. 


ANALYSIS OF LITHARGE 
SCHAEFFER METHOD 


Litharge, the monoxide of lead, PbO, may contain small per- — 


centages of iron, copper, silica, silver and free metallic lead. 


When the litharge has been made by a process where steam is — 


used, there may be an appreciable amount of moisture present. 
It appears on the market in two colors, yellow and red. In 
some instances litharge is found containing a comparatively 


large percentage of red lead, which in certain uses is undesir- — 


able. The determination of each of the foreign constituents in 
litharge depends largely upon the use to which the litharge is to 
be put, as in very few cases are all the constituents determined. 

Moisture.—Dry 2 grams of the sample at 105° C. for two 
hours. The loss will be moisture. 

Free Metallic Lead.—Two grams of the sample are treated 
in a beaker with hot water and just sufficient acetic acid is 
slowly added, to dissolve the lead oxide. Stir the solution well 
and note whether any lead silicate remains undissolved. Should 
such remain, continue stirring until solution has been effected. 
The solution should never have greater than a 5-per-cent acetic 
acid strength. 

Filter the solution and wash the residual metal three or four 
times by decantation with hot water, having all the wash water 
pass through the filter paper, which is finally thoroughly washed 
with hot water. Transfer any metal on the filter paper to the 
beaker containing the residual lead, add 1 ce. of concentrated 
nitric acid and heat to solution. Dilute with 50 ec. of water, add 
1 gram of sodium acetate and follow this with an excess of 


saturated neutral potassium bichromate solution, sufficient to 


precipitate all the lead. Boil, dilute to 100 cc., allow to cool, 


Ch, ae ee ae a NT 


[ae eae 
pe ee See, Ve ee 


ANALYSIS OF LEAD OXIDES 345 


filter off the lead chromate, wash thoroughly and determine the 
lead chromate gravimetrically by drying at 100° C. or volumet- 
rically by titration of the chromic acid present as outlined un- 
der the analysis of Basic Sulphate of Lead. For the direct de- 
termination of lead in this case the factor to divide by is 2, as a 
2-gram sample is used. 

Red Lead.—Determine the percentage of red lead present as 
outlined under the Analysis of Red Lead. 

Iron.—Treat 1 gram of the sample with 10 cc. of water and 
just sufficient nitric acid, added drop by drop, to cause com- 
plete solution. Heat to boiling to oxidize all the iron and de- 
termine it colorimetrically. 

Copper.—Copper may be rapidly and accurately determined 
by the method described on page 335. The following gravimetric 
method, however, may be found more convenient if only a few 
determinations are to be made. 

Twenty grams of the litharge contained in a 200-cc. flask are 
dissolved in nitric acid (50 cc. concentrated nitric acid to 100 
ec. water). Boil to complete solution. Add 40 cc. of dilute sul- 
phuric acid (1:1), boil gently for one hour and allow to cool. 
Filter off the lead sulphate and wash the precipitate thoroughly. 
Nearly neutralize all the free acid present with ammonium 
hydroxide, render slightly acid with hydrochloric acid, warm 
the solution and pass in hydrogen sulphide until no further pre- 
cipitation of suphide occurs. Filter off the precipitate with- 
out washing, using some of the filtrate to transfer the last traces 
of sulphide to the filter paper. Dissolve the precipitate in a little 
nitric acid and wash the filter paper thoroughly with hot water. 
Add 8 cc. of concentrated sulphuric acid, evaporate until the 
white fumes of sulphuric acid are evolved and allow the solu- 
tion to cool. Add a little water and allow to stand for some 
hours. Filter off the lead sulphate, washing with hot water 
containing a little sulphuric acid. 

Heat the filtrate to boiling and precipitate the copper as sul- 
phide with hydrogen sulphide in an ammoniacal solution. Filter 
off the copper sulphide through an ashless filter paper, wash, 
ignite and weigh in a covered porcelain crucible, from which 
the heat and cover are occasionally removed for a few seconds. 

The precipitate will consist of a mixture of CuO and Cu,S. 


346 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Since the percentage of copper is the same in both of these, the 
copper may be determined by multiplying the amount found by 
the factor 0.7988. 


Silica.—Digest 5 grams of the sample in a covered casserole ~ 


with 2 grams of potassium chlorate and 15 ec. of dilute nitric 
acid (1:1). Evaporate to dryness and dehydrate. Treat the 
residue, after cooling, with hot water and nitric acid. Heat to 
boiling, and filter the solution through an ashless filter paper. 
Wash the residue and filter paper thoroughly with hot acid 
ammonium acetate solution, made up to a strength as outlined 
on page 310. Should the residue show a trace of iron, wash it 
thoroughly with dilute hydrochloric acid. Complete the wash- 
ing with hot water, dry, ignite and weigh as SiO,. The residue 
may be volatilized with hydrofluoric acid, if there is any doubt 
regarding the purity of the silica. 

The silica is present as lead silicate and free silica. The above 
method determines the total content of silica. The free silica 
may be determined by dissolving the litharge in dilute nitric 
acid. Heat to boiling, filter, wash, ignite and weigh as silica. 


ON ee eee ee 


bs 
3 
‘ 
‘ 


CHAPTER XXXVII. 


ANALYSIS OF VERMILIONS 


The following portion of Walker’s* method, will suffice for the 
examination of Mercury Vermilion. Should the analyst desire 
to determine the sulphide of mercury present or make a more 
complete examination—reference may be made to the original 
method. 

True vermilion, or, as it is generally called, English ver- 
milion, is sulphide of mercury. On account of its cost it is 
rarely used in paints, and is liable to gross adulteration. It 
should show no bleeding on boiling with alcohol and water and 
no free sulphur by extraction with carbon disulphide. A small 
quantity mixed with five or six times its weight of dry sodium 
carbonate and heated in a tube should show globules of mercury 
on the cooler portion of the tube. The best test for purity is the 
ash, which should be not more than one-half of 1%. Make the 
determination in a porcelain dish or crucible, using 2 grams 
of the sample. Ash in a muffle or in a hood with a very good 
draft, as the mercury fumes are very poisonous. It is seldom 
necessary to make a determination of the mercury. Genuine 
mercury vermilion is at the present time little used in paints. 
Organic Reds.—Organic lakes are used for most of the bril- 
-jiant red, scarlet and vermilion shades. These organic coloring 
matters are sometimes precipitated on red lead, orange mineral 
or zinc oxide; but as a usual thing the base is barytes, whiting 
or china clay. Paranitraniline red, a compound of diazotized 
paranitraniline and beta-napthol, is largely employed; but a 
number of colors may be used. The examination of these reds 
follows the method as communicated to the writer by BE. F. Hick- 
son. 

Qualitative Tests for Reds.—In qualitatively testing ver- 
milions (para red, toluidine red, and lithol red) the following 
suggestions may be useful: (1) Para Red. The intense purple 
eolor in a mixture of alcohol (ethyl or denatured) and sodium 
hydroxide solution distinguishes para red from the other two. 


* P, H. Walker, Miscellaneous Publications, No. 15, U. S. Bureau of 
Standards, p. 32. 


347 


348 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


oe eee 


(2) Toluidine and Lithol Reds. (a) Chloroform Test.—A small 


amount (0.1 g. or less) of C.P. toluidine red, when stirred into _ 


100 ce. of warm chloroform, gives a practically clear, orange red 


Solution within one hour. Lithol red under the same conditions 
remains practically undissolved, even overnight, giving a nearly © 


colorless filtrate. (b) Sodium Carbonate.—C.P. toluidine red is 3 


exceptionally resistant to strong alkalies and acids. A boiling 
solution of fairly strong sodium carbonate will have practically 
no effect on the bright orange red color of the toluidine, whereas 


the lithol red (barium lake), will be converted to the sodium _ 


salt; make both liquids slightly acid with dilute sulphuric acid 
and without filtering, place a piece of clean, freshly washed wool 
in each, and allow to remain for 10 minutes. Take each piece 


of wool and wash thoroughly with mild soap and water, taking ‘ 


care to wash off any absorbed pigment particles. The lithol 
dyes the wool a fast, uniform pink (coral) color that will not 
wash out; the toluidine does not dye the wool. 


Percentage of Pigment in Paste or Paint.—Weigh accurately — 


about 15 g. of the paste or paint into a weighed centrifuge tube. 
Add 20 to 80 ce. of petroleum ether, mix thoroughly with a glass 
rod, wash the rod with more of the petroleum ether, and add 
sufficient of the reagent to make a total of 60 cc. in the tube. 
Place the tube in the container of a centrifuge, surround with 
water, and counter-balance the container of the opposite arm 
with a similar tube or a tube with water. Whirl at a moderate 
speed until well settled. Decant the clear supernatant liquid. 
Repeat the extraction twice using petroleum ether. After draw- 
ing off the last extract, set the tube on top of a warm oven for 
10 minutes, then in an oven at 110 to 115° C. for two hours. 
Cool, weigh, and calculate the percentage of pigment. Grind 
the pigment to a fine powder, pass through a No. 80 screen to 
remove any skins, and keep in a stoppered bottle. 

Analysis of Pigment.—Test the pigment first qualitatively. 
Place a small portion of the pigment in a 50 ec. beaker and add 
about 25 cc. of alcoholic KOH or NaOH. Para-red will turn a 
dark reddish purple. Pour off the colored solution, and repeat 
until all the color is in solution and a white base remains. Add 
a little HNO, to some of the base to show the presence of car- 
bonate. A white base, giving no effervescence or test for CO,, 


ee ee a ee ee ee 


ANALYSIS OF VERMILIONS 349 


is probably composed of silicates or silicate and barium sulphate. 
Occasionally the base contains orange mineral; the addition of 
HNO, will turn this pigment brown and bleach out on adding 
a few drops of dilute NaNO, solution. 

Percentage of color.—wWeigh accurately about 0.5 g. portion 
of the pigment into a 250 cc. beaker, add about 100 ce. of warm 
chloroform, and stir with a glass rod, breaking up any lumps. 
Decant the colored solution through a weighed Gooch crucible, 
and leave the residue in the beaker. Add a 50 cc. portion of 
chloroform to the residue and stir well with a glass rod, break- 
ing up any lumps. Decant the colored solution through the 
Gooch crucible and repeat the washing of the residue in the 
beaker with 50 ce. more of chloroform. Finally transfer the 
residue onto the Gooch crucible, and continue the washing with 
chloroform from a wash bottle until the base is white or the 
washings colorless. Dry the Gooch crucible at 105-110° C. to 
constant weight and report the loss as “‘pure color.” 

NoTe.—In case the examination of the pigment shows calcium carbonate 
to be absent and the base to be barium sulphate and silicates, a direct loss 
on ignition using 1 g of the sample will generally check the above within 
0.5 per cent. 

In case the base contains calcium carbonate, hydrated clays, 
alumina, etc., an ignition loss can not be calculated to organic 
color, since the results are too high, due to loss of combined 
water in the clay. 

The above method for percentage of color will give in most 
cases a base free from organic color with about 250-300 cc. of 
chloroform. 

Some samples have been washed with the following mixture 
for the percentage of color and satisfactory results were ob- 
tained: 


10 vol. ethyl ether 
6 vol. benzol 
4 vol. methyl alcohol 
1 vol. acetone 


Make alkaline with NaOH 


This is followed with alcoholic NaOH, alcohol and ether. 

In separating the pigment from the vehicle, petroleum ether 
has been found to dissolve out only a slight amount of organic 
color. 


300 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


Another suggested solvent for separating the pigment from 
vehicles is a mixture of two-thirds to three-quarters petroleum 
ether and one-third to one-quarter ethyl ether. Benzol or the 
mixed solvents mentioned above do not work well with some 
samples of vermilion paint. The reader is also referred to Fed- 
eral Specification Board Specification No. 66 for Red Knamel, 
in the back of this book. 


Ee ee ae a ae ee can eee 


CHAPTER XXXVIII. 


ANALYSIS OF INDIAN REDS, RED OXIDES 
(PRINCE’S METALLIC, TUSCAN RED, ETC.) 


Added Coloring Matter.—Test the pigment successively with 
hot water, 95 per cent ethyl alcohol, alcoholic NaOH or KOH and 
acetic acid. Chloroform, NaOH, H.SO, HCl-stannous chloride, 
and other reagents may be tried.* The presence of an organic 
color may often be noted by the characteristic odor given off 
on ignition. 

Loss at 100° C.—Heat 2 g. in a steam-jacketed oven at atmos- 
pheric pressure for three hours, or to constant weight. 

Loss on Ignition.—Ignite a portion in a covered porcelain 
crucible to constant weight. This may include combined water, 
CO.,, organic matter, and some SO, if much CaSO, is present. 
CO, may be determined on a separate portion of the sample if 
desired.t 

Free Acid or Alkali.mBoil 10 g. of sample with 100 cc. of 
water; filter and wash. Test filtrate with litmus paper; if acid, 
titrate with standard alkali and methyl orange and calculate to 
the equivalent of H,SO,. If alkaline, titrate with acid and cal- 
culate to the equivalent of Na,O. Test filtrate for alkali salts 
and alkaline earths. 

Insoluble, Iron Oxide, Etc.—Digest 2.5 g. of the sample (previ- 
ously roasted at a low temperature if much organic matter is 
present; if very low in carbonaceous matter a little KC1O, or 
NaClO, may be used in effecting solution) with 25 cc. of HCl 
(adding a little HNO, or chlorate, if not already added), wash 
off cover, and evaporate to dryness. Take up with HCl and 
water, filter, wash with dilute HCl and cold water. Make the 
filtrate up to 500 cc., mix, and examine as below.{ Ignite the 


* For details consult Zerr, “Tests for Coal-Tar Colors in Aniline Lakes,” 
(English translation by C. Meyer); Schultz and Julius, “A Systematic 
Survey of the Organic Coloring Matters’; Hall, “The Chemistry of Paints 
and Paint Vehicles”; and Mulliken, “Identification of Pure Organic Com- 
pounds,” Commercial Dyestuffs, Vol. III. 

+ It is inadvisable to use platinum unless it is known that attacking sub- 
stances are absent. 

+ For more exact work this filtrate should be evaporated to dryness and 
SiO. removed. 


351 


352 EXAMINATION OF PAINTS, VARNISHES AND COLORS - 
SS 


residue and weigh as “insoluble matter;’§ if this contains — 
BaSO, it may be determined by fusing with six times its weight — 
of Na,CO,, cooling, digesting with hot water, filtering, and wash- E 
ing the residue with hot water until free of sulfate. a 
Remove filtrate and place beaker used for the digestion under. oe 
neath the funnel, pierce the filter with the glass rod, and wash — 
the residue with a little water into the beaker; then pour hot — 
dilute HCl (1:1) over paper, and finally wash with hot water. ‘ 
If necessary add more HCI to the beaker to dissolve the BaCO,; 
heat to boiling, add dilute H,SO, in slight excess, let stand about 
one hour on steam bath; filter, wash, dry, ignite, and weigh 
BaSO,. (This subtracted from total insoluble will give “‘in- 
soluble silicious matter,” if it is desired to so report.) If it is 
desirable to analyze the insoluble silicious matter, this can be © 
done by the usual methods for silicate analysis, but the results 5 
should be reported as a separate analysis. } A 
For the determination of iron place 100 ce. of the first filtrate 
in a flask, add about 3 g. of granulated zine, put a funnel into . 
the neck of the flask, heat when the action slackens; if basic — 
salts separate out add a few drops of HCl. When the reduction ¢ 
is complete, add 30 ec. of H,SO, (1:2), and as soon as the 
residual zine is dissolved, wash down the funnel inside and out 
and the neck of the flask with a fine jet of water, filling the 
flask (1000 ce.) about two-thirds full, cool in water, add 10 cc. 
of “titrating solution” (made by dissolving 160 g. of manganese 
sulfate in water, diluting to 1750 cce., adding 330 cc. of HeEvO} 
Sp. gr. 1.72, and 320 ce. of concentrated H,SO,), and titrate with 
KM..9,. (5.659 g. per liter) that has been standardized against 
Bureau of Standards sodium oxalate. Run a blank on the zine, 
correct for same and calculate total iron as Fe,O,. Instead of 
adding the zinc to the solution, the reduction may be effected in 
a zine reductor.* 
The Fe,0, may also be determined by the K,Cr,O, method. 
Lime.—Dilute an aliquot of 100 ce. of the original solution to 
about 200 ce., add 10 ce. of HCl, make alkaline with NH,OH, @ 
add 2 or 8 ec. of bromine water, and boil till excess of NH, is. .@ 


" 


Pee en) a eee en a ee 


§ If the insoluble contains appreciable amounts of Fe it will be necessary — 

to fuse it with Na.CO, or K.S.0; to determine total Fe in samples. ee 
‘§ Lord and Demorest, “Metallurgical Analysis,” 1918, pp. 28-29. 
¢ Ibid., pp. 21-26. 


ANALYSIS OF RED OXIDES 300 


expelled. Let settle, wash by decantation, redissolve in HCl, 
and reprecipitate with NH,OH and bromine water. (Precipi- 


y 


tate = Fe,O,.Al,0,.TiO, .P,0O,.MnO,.) This precipitate may be 
ignited and weighed if desired. 
To the combined filtrates add a few drops of NH,OH, heat to 


oiling, and add an excess of saturated ammonium-oxalate solu- 
- ion; continue the boiling until the precipitate becomes granular, 


‘et stand about 30 minutes, filter, and wash with hot water till 
free of ammonium oxalate,* place beaker in which precipitation 
“was made under the funnel, pierce apex of filter with stirring 
rod and wash precipitate into beaker with hot water, pour 
warm dilute H,SO, (1:4) through paper and wash a few times; 
add about 30 cc. of H,SO, (1:4), dilute to about 250 cc., heat 
to 90° C. and titrate at once with standard KMn0O, solution 
(solution should not be below 60° C. when end-point is reached). 
Calculate to CaO. (The Fe value of KMnO, x 0.502 = CaO.) 
The calcium-oxalate precipitate may be ignited to constant 
weight as CaO. If desired, magnesia may be determined as 
Mg,P,0, in the usual manner in the filtrate from the calcium 
oxalate. t 

Soluble Sulfates.—Treat 1 g.t of the pigment (roasted gently 
if much organic matter is present) with 30 cc. of HCl, boil 10 © 
minutes, add about 50 cc. of water, boil, filter, and wash with 
hot water. Heat the solution to boiling, add NH,OH, filter 
and wash a few times with hot water; dissolve precipitate in 
hot dilute HCl and reprecipitate with NH,OH, wash well with 
hot water. Render united filtrates just distinctly acid with HCl, 
boil, add by drops with stirring excess of 10 per cent BaCl, 
solution, boil about 10 minutes, filter on a Gooch crucible, wash 
with hot water, ignite and weigh as BaSO,. Calculate to SO, 
or CaSQ,. 

Total Sulfur other than that Present as BaSO,.—Treat 5 g. 
of the sample in a covered porcelain dish with 50 cc. of aqua 


* For more exact work this precipitate should be dissolved in HCl and 
the calcium oxalate reprecipitated as above. 

7 If desired, a direct determination of Al,.O; may be made on an aliquot 
of the solution or on the HCl solution of the NH.OH precipitate by Peters’ 
phosphate method (this will include titanic acid) as described by Blair, 


“The Chemical Analysis of Iron,” and Philips, “Methods of Iron Analysis 
Used in the Pittsburgh District.” 
; {If low in soluble sulfates use a larger portion of sample. 


; ’ 


354 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


regia (LHNO,:9 HCl) and evaporate to dryness on steam bath. 
Add 20 ec. of concentrated HCl and about 250 cc. of water, make 
double NH,OH precipitation; determine BaSO, as given under 
“Soluble Sulfates.”’ 

Cuprous Oxide Red in Antifouling Paints.—The red cuprous 
oxide used in antifouling paints can be analyzed in accordance 
with the following method. Weigh accurately about 0.25 g. of — 
the dry sample into a 250-ce. ground glass stoppered Erlenmeyer 
flask. Add 10-15 cc. of acid ferric chloride solution (200 g. 
FeCl,. 6 H,O in 500 cc. of 1:1 HCl), and a few glass beads, stop- — 
per, and rotate until the oxide is completely dissolved (usually 
within 2 or 3 minutes on high-grade finely ground samples). 
Warm on the steam bath, if necessary, but it is not advisable and 
generally unnecessary. Add 5 cc. of syrupy phosphoric acid, 
200 cc. of cool distilled water, and titrate the ferrous iron with 
decinormal KMn0O, to the first permanent (30 seconds) color 
change. A blank (usually about 3 drops) should be run on the 
reagents. 


1 cc. O. 1 N KMn0O, = 0.00636 g. Cu. 
= 0.00716 Cu,O 


CHAPTER XXXIX. 
ANALYSIS OF OCHERS 
(SIENNAS, UMBERS, ETC.) 


Loss at 100° C., loss on ignition, insoluble matter, total or 
soluble iron, alumina, lime and sulfur may be determined as 
outlined under the ‘‘Methods for Analysis of Indian Reds, etc.,” 
using 1 g. or an aliquot corresponding to this weight. 

Lead Chromate.—If present, the lead is removed in the above 
scheme by nearly neutralizing the filtrate from the insoluble 
matter with NH,OH, cooling, and passing in H.S, to precipitate 
PbS. Filter, wash with water, containing H.S, dissolve PbS 
in hot dilute HNO,, add 10 cc. of concentrated H,SO,, evaporate 
till SO, is evolved, cool, dilute to 200 cc., let stand a few hours, 
filter on a Gooch crucible, wash with 1 per cent H,SO,, ignite, 
and weigh PbSO,. Calculate to PbO or Pb. Heat the filtrate 
from the PbS to expel H,S, oxidize with a little HNO., and make 
up to volume if working on more than 1 g. 

The iron is best determined in an aliquot by the K,Cr.,O, 
method. Another aliquot is treated with NH,OH, the precipi- 
tate containing AI,O,.Fe,0,.Cr,0;.P,0,.TiO,. Lime and MgO 
may be determined in filtrate. | 

The NH,OH precipitate is dissolved in hot dilute HCl, wash- 
ing paper with hot water, cooled, oxidized with Na,O., boiled 
to expel H,O,, cooled, cover glass washed off, diluted to about 
150 cc., and acidified with H,SO,. Add a measured excess of 
ferrous ammonium-sulfate solution — (NH,),Fe(SO,).,.6H,O, 
12.4 g.; concentrated H,SO,, 50 cc.; and water to make 1 liter, 
and titrate back with standard K,Cr,O, solution to determine 
its value in terms of the latter. The Fe value of the K,Cr,O, 
solution « 0.5969 = CrO.. 

Or, moisten 1 g. of the pigment with water, add 5 cc. of con- 
centrated HCl, boil a few minutes, cool, add Na,O, in excess, 
boil to expel H,O., cool, wash off cover glass, dilute, acidify with 
H.SO,, and titrate CrO, as above. 


ANALYSIS OF VENETIAN RED 


Analyze as given under “‘Method for Analysis of Indian Reds, 
etc.” Insoluble matter may be treated with HF and H.SO, to 
determine SiO, by loss if desired. 


355 


356 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


ANALYSIS OF SIENNAS AND UMBERS 


After gently roasting to destroy organic matter, test as given 
under “Methods for Analysis of Indian Reds, etc.” 

Manganese.—Manganese is determined by the bismuthate | 
method.* Ignite gently (to destroy organic matter) 1 g. of the © 
sample in a platinum dish, cool, add 10 cc. of water, 4 cc. of 
concentrated H,SO, and about 20 cc. of HF (if necessary, add — 
a little sulfurous acid). Evaporate until the H,SO, fumes freely, — 
cool and dissolve in 25 ec. of HNO, (1 part concentrated HNO, 
to 3. parts water). If no appreciable residue remains, transfer — 
to a 100-cc, volumetric flask, using 25 ec. of HNO, (1:3) to — 
rinse the dish, dilute to the mark with water, mix thoroughly. — 
If there is an appreciable residue, filter on a small filter, wash 
with water, ignite residue in a platinum crucible, and fuse with 
a little sodium or potassium pyrosulfate. Dissolve in water, 
with the addition of a little HNO,, add to the main filtrate, 
evaporate nearly to dryness, take up in HNO, (1:8) and trans- 
fer to the flask as before. Pipette an aliquot of 10 cc. into a 
200-cec. Erlenmeyer flask, add 30 cc. of water and 10 cc. of con- 
centrated HNO., sp. gr. 1.4; add about 0.5 g. of sodium bis- 
muthate, heat for a few minutes, or until the pink color has dis- 
appeared with or without the precipitation of MnO,. Add a 
few small crystals of sodium or potassium nitrate to dissolve — 
the MnO, and boil the solution several minutes to expel nitrous 
fumes (a little Na,CO, will aid this). Add water to bring the 
volume up to 50 cc. and cool to about 15° C.; add about 0.5 g. — 
of bismuthate and shake the flask well. Add 50 cc. of water 
containing 30 cc. of concentrated HNO, to the liter, filter by suc- 
tion through an asbestos felt into a 300-cc. Erlenmeyer flask 
and wash with 50 to 100 cc. ofthe same acid. Run in a meas- 
ured volume of standard ferrous ammonium-sulfate solution and 
titrate to a faint pink color with standard KMnO, solution. The 
number of cubic centimeters of the KMnO, solution obtained, 
subtracted from the number corresponding to the volume of 
ferrous solution used, will give the volume of KMnO, equivalent 
to the manganese in the sample, which, multiplied by the value 
of the KMnO, in Mn, gives the weight of manganese in the por- 
tion of sample used. 


* Blair, “The Chemical Analysis of Iron.” 


OCHRES 357 


Standard KMnO, Solution —tThe solution of KMnO, is com- 
posed of 1 g. dissolved in a liter of water. The Fe value of this 
solution X 0.1968 = Mn. This solution may be _ standardized 
against Bureau of Standards sodium oxalate (using about 0.05 
to 0.1 g.)* Weigh of Na,C,O, x 0.1639 = Mn. Twelve grams 
of (NH,).Fe(SO,),.6H,O, 25 cc. of concentrated H,SO,, and 25 
cc. of H,PO,, sp. gr. about 1.7, are made up to 1 liter with water. 
The value of this solution should be determined against the 
KMn0O, each day as follows: 

Measure into a 200-cc. Erlenmeyer flask 50 cc. of HNO, 
(1:3), cool, add a little bismuthate, dilute with 50 cc. of 3-per- 
cent HNO.,, filter by suction through an asbestos felt into a 
300-cc. Erlenmeyer flask, and wash with 50 cc. of 3-per-cent 
HNO,. Run in 25 ec. of the ferrous solution and titrate with 
KMn0O, solution. Instead of titrating the permanganic acid 
formed by the bismuthate with the ferrous solution and then 
titrating back with KMn0O,, a direct titration with standard 
sodium arsenite solution may be made.t 


*W. Blum, “Original Communications, Eighth International Congress 
of Applied Chemistry,” Vol. I, pp. 61-85. 
+ Lord and Demorest, “Metallurgical Analysis,” 1913, p. 82. 


CHAPTER XL. 


ANALYSIS OF YELLOW. AND ORANGE PIGMENTS 


CHROME YELLOWS, AMERICAN VERMILION, BASIC LEAD 
CHROMATE 


A pure chrome yellow should contain only lead chromate and . 
other insoluble lead compounds. 

Added Coloring Matter.—Test the pigment successively with 
hot water, 95-per-cent ethyl alcohol, and chloroform. The solu- 
tions should remain colorless. Other reagents may be tried.* 

Moisture.—Heat 2 g. at 105° C. for two hours. The loss in 
weight is reported as moisture. 

Insoluble Matter.—Treat 1 g. with 25 cc. of concentrated HCl 
and boil for from 5 to 10 minutes in a covered beaker adding 
about 6 drops of alcohol to the boiling liquid, one at a time. 
Dilute to 100 cc. with hot water and boil for from 5 to 10 min- 
utes (the solution should be complete). Filter the hot solution 
(if insoluble matter is present) and wash with boiling water 
till washings are free from lead and chlorine. Ignite the insolu- 
ble matter, weigh, and examine for SiO,, BaSO,, and Al1,O,. | 

Total Lead.—Nearly neutralize with NH,OH the filtrate from 
the insoluble matter (or the original solution), dilute to about 
300 cc., and pass into the clear solution a rapid current of H,S 
until all of the lead is precipitated as PbS. Let the precipitate 
settle, filter, wash with water containing some H.S. Boil the 
filter and precipitate with dilute HNO, until all of the lead has ~ 
dissolved, filter, and wash thoroughly with hot water. To the — 
filtrate, add 10 cc. of H,SO, (1:1), evaporate until copious 
fumes of SO, are evolved, cool, add about 75 cc. of H,O and then 
75 ec. of 95-per-cent ethyl alcohol. Let stand about one hour, — 
filter on a Gooch crucible, wash with dilute alcohol, dry, ignite, 
and weigh as PbSO,. 

Chromium (Iron, Aluminum) .—Heat the filtrate from the 
PbS to expel H.S and, if iron is present, add a few drops of 

* For details consult Zerr, “Tests for Coal-Tar Colors in Aniline Lakes” 
(English translation by C. Mayer) ; Schultz and Julius, “A Systematic Sur- 
vey of the Organic Coloring Matters’; Hall, “The Chemistry of Paints and 


Paint Vehicles”; and Mulliken, “Identification of Pure Organic Compounds,” 
Commercial Dyestuffs, Vol. ITI. 


358 


ORANGE AND YELLOW PIGMENTS 359 


HNO, and boil about two minutes. Render the solution just 
alkaline with NH,OH, boil a few minutes, filter, and wash with 
hot 2-per-cent NH,Cl solution. (If the sample contains an 
appreciable amount of zinc, a double precipitation should be 
made.) In the absence of iron and aluminum this precipitate 
may be ignited and weighed as Cr,O,. If iron and aluminum are 
present, dissolve the NH,OH precipitate with hot dilute HCl, 
washing the paper with hot water; cool, add NH,OH until alka- 
line, and then add Na,O, (about 1 g.), keeping the beaker cov- 
ered. Digest until all of the chromium and aluminum have been 
dissolved, adding more Na,O, if necessary. Filter off the 
Fe(OH),, wash thoroughly with hot water, ignite and weigh 
as Fe,O,; or, dissolve the precipitate in HCl and determine the 
Fe content volumetrically. Make up the filtrate from the 
Fe(OH), to 250 ce. in a graduated flask, and mix. Render an 
aliquot portion acid with H,SO,, boil to expel any free oxygen, 
cool, add an excess of standard (NH,).Fe(SO,)..6H,O solution 
and titrate back with N/10 K,Cr,0, solution, using K,Fe(CN), 
as outside indicator. (The CrO, may also be determined by 
acidifying the aliquot portion with acetic acid, precipitating as 
PbCrO, or BaCrO,, and finally weighing on a Gooch crucible.) 
To determine Al,O,, make an aliquot portion of the filtrate from 
the Fe (OH), acid with HCl, and then just distinctly alkaline 
with NH,OH, heat to boiling, let settle, filter, wash with hot 2- 
per-cent NH,Cl solution, ignite and weigh as Al,O,. If iron and 
aluminum are not to be determined or are present in negligible 
amounts, the first NH,OH precipitate may be dissolved in dilute 
HCl, oxidized with Na,O., acidified with H,SO,, boiled, and CrO, 
determined volumetrically. The CrO, in the absence of other 
Oxidizing substances, may be determined on 1 g. of the pigment 
by Schwartz’ method (Fresenius Quantitative Chemical An- 
alysis, Ed. 6, Vol. 1, p. 424). 

Zinc, Calcwm, and Magnesium.—Precipitate any zinc in the 
filtrate from the first NH,OH precipitate with H,S, filter, wash 
with dilute (NH,).S, dissolve the zine sulfide in dilute HCl, 
and determine the Zn content volumetrically by K,Fe(CN), 
method. In the filtrate from the zine sulfide, determine calcium 
by the oxalate method and magnesium as Mg.,P.0.. 

Sulfuric Anhydride.—Heat 1 g. of the pigment with 10 cc. of 
concentrated HCl until free chlorine is expelled, add about 300 


360 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


ec. of water and boil; filter off any insoluble matter and wash 
thoroughly with hot water, heat to boiling, and precipitate with 
BaCl, solution in the usual manner. Keep the solution hot while 
filtering off the BaSO, and wash with hot water until the wash- 
ings show no lead or chlorine. 

Carbon Dioxide.—Determine carbon dioxide by the evolution 
method, using dilute HNO.,, free from oxides of nitrogen. 

Water-Soluble Matter.—Weigh 5 g. of the pigment on to a 
weighed Gooch crucible (containing asbestos, and dried at 110° 
C.), wash six times with 25-cc. portions of cold water; dry at 
110° C. and weigh. The loss in weight, corrected for moisture 
(as determined above), represents the soluble salts removed by 
the water. The washing may be examined, if desired. 

Calculations.—Calculate CrO, to PbCrO,, and SO, to PbSO, 
if calcium is absent. If CO, is present and calcium and man- 
nesium are absent, calculate to (PbCO,),.Pb(OH).. Report 
any residual Pb as PbO. If calcium is present, calculate to 
CaCO, if CO, is also present. If calcium and SO, are present 
and CO, is absent, calculate to CaSO,. If calcium, CO,, and SO, 
are present, calculate to CaCO,; any residual calcium is then 
calculated to CaSO,. Report zinc as ZnO. 


CADMIUM LITHOPONE 


This pigment is a chemically precipitated pigment containing 
approximately 68 per cent barium sulphate, the balance consist- 
ing principally of yellow cadmium sulphide with some zinc sul- 
phide. It is not affected by hydrogen sulphide. For moisture, 
water soluble, total sulphides, and oxides, see methods for litho- 
pone. 

Method for Cadmium and Zine Sulphides.—Take 1 gram of 
the sample in a 200 cc. beaker, add 15 cc. of concentrated HCl, 
mix, and add in small portions about 1 g. KCIO,, then heat on 
the steam bath until about half of the liquid is evaporated and 
the yellow color of the CdS has disappeared. (If necessary, a 
few ce. of concentrated HNO, may be added at this point to ef- 
fect the solution of the CdS.) Then add 15 ce. of 1-1 sulphuric 
acid and evaporate to fumes of SO,. Cool, dilute with 100 cc. of 
water, filter off, and weigh the insoluble barium sulphate and 
examine it for alumina and silica (not likely to be present). 

To the filtrate from the insoluble, add water until volume is 
200 cc. Cool and pass a rapid stream of H,S gas through the so 


ORANGE AND YELLOW PIGMENTS 361 


lution for 15 minutes. Add dilute NH,OH, drop by drop until 
yellow cadmium sulphide begins to precipitate. Heat the solu- 
tion to about 90° C. and again pass H.S for five minutes. Boil the 
solution for a few minutes, let settle, and filter through close- 
grained paper, washing the precipitated CdS with cold 10% sul- 
phuric acid and with hot water. Save filtrate for zinc. 

Dissolve the sulphide on the filter in 1-2 HCl in a clean beaker, 
add 15 cc. (1-1) sulphuric acid, take to fumes, and repeat pre- 
cipitation of CdS. Filter through weighed Gooch crucible, wash 
with 10% sulphuric acid and hot water, dry at 110° C. for one 
hour, and weigh as CdS. 

Combine the two filtrates from the CdS precipitation cool 
thoroughly, make slightly alkaline with NH,OH, and pass a rapid 
stream of H,S gas for ten minutes. Heat to boiling, let settle, 
filter on fine-grained paper, wash well, and ignite carefully in 
crucible to ZnO. Factor ZnO to ZnS = 1.1975. 


CHAPTER XLI. 


ANALYSIS OF BLUE PIGMENTS 


IRON CYANIDE BLUES. (PRUSSIAN BLUE, CHINESE BLUE, 
ANTWERP BLUE, MILORI BLUE, BRONZE, BLUE, 
STEEL BLUE.) 


The analysis of these blues, as is generally the case with pig- 
ments, does not necessarily give results which can be used to 
grade samples, the strength and color tests being most impor- 
tant. 
Movrsture.—Heat 2 g. of the pigment at 105° C. for two hours. 
The loss in weight is reported as moisture. A “dry” Prussian 
blue should contain less than 7 per cent of moisture. 

Insoluble Matter.—Ignite 1 g. of the pigment in a porcelain 
dish at a low temperature, just high enough to decompose the 
last. trace of blue, but not high enough to render the iron diffi- 
cultly soluble in HCl. Cool, add 15 cc. of HCl and a few drops of 
bromine, cover with a watch-glass, and digest on the steam 
bath; wash off cover, evaporate to a syrup, add water, boil, 
filter, wash with hot water, ignite the residue and weigh. 
Examine the insoluble residue for silica, barium sulfate, and 
alumina. A pure Prussian blue should show no insoluble residue. 

Iron and Aluminum.—Determine iron and aluminum in the 
filtrate from the insoluble matter by precipitation with NH,OH 
in the usual manner. A double precipitation is desirable. Ignite 
and weigh Fe,0,-+ Al,O,, deduct Fe,O, (calculated from total 
Fe), and calculate Al,O, to Al. 

Calcitum.—Determine calcium in the filtrate from the Fe,0, 
+ Al,O, by precipitation with ammonium oxalate ; titrate with 
KMn0O,, or, ignite and weigh as CaO. Acidify the filtrate from 
the calcium oxalate with HCl and dilute to a definite volume and 
mix. 

Sulfuric Acid.—Determine sulfuric acid in an aliquot of the 
above solution as BaSO, in the usual manner. 

Alkali Metal and Alkaline Salts.—Evaporate an aliquot of 
the above solution with sulfuric acid, ignite (treating with solid 
ammonium carbonate), and weigh. Determine whether the 
alkali metal is sodium or potassium and subtract the alkali metal 


362 


Oa 


BLUE PIGMENTS 363 


corresponding to the sulfate (SO,) found. The remainder is 
alkali combined with the blue and is reported as Na or K. 

Total Iron—Decompose and dissolve 1 g. of the pigment as. 
under “Insoluble Matter,” reduce, and determine the total iron 
with KMnO, or K,Cr,0,. There should be not less than 30 per 
cent, calculated on the dry pigment. 

Total Nitrogen.—Determine the total nitrogen on a 1-g. sam- 
ple of the pigment by the Kjeldahl-Gunning Method, digesting 
for at least 214 hours. The sulfuric acid should not blacken, 
which would indicate organic adulteration. 

Water-Soluble Matter.—Weigh 2.5 g. of the pigment into a 
graduated 250-cc. flask, add 100 cc. of water, and boil for five 
minutes. Dilute with water, let stand until at room tempera- 
ture, make up to mark, mix and let settle. Filter through dry 
paper and discard the first 25 cc. Transfer 100 cc. of the clear 
filtrate to a weighed dish, evaporate to dryness on a steam-bath, 
ary in-an oven at 105° C. for 30 minutes, cool and weigh. 

Calculations —The percentage of Prussian blue may be ob- 
tained with sufficient accuracy for commercial purpuses by mul- 
tiplying the percentage of nitrogen by 4.4 or the percentage of 
iron (in the absence of other iron pigments) by 3.03.* 


NoTEe.—Some blues, e. g-, Chinese blue, may contain tin salts. Others 
may contain manganese or chromium compounds. The presence of these 
compounds should be determined by a qualitative examination at least. 


Heckel Method for Iron in Prussian Blue.—In a method for 
the examination of Prussian blue, worked out by James E. 
Heckel, the sample is heated in an open crucible, gently at first 
and later with strong heat. The contents of the crucible are 
then brushed into a beaker, also placing the crucible in the 
beaker if any of the Fe,O, clings to it. Heat with 25 cc. con- 
centrated HCl and add 3 cc. SnCl,. In about fifteen minutes 
solution is complete. If the crucible has been placed in the 
beaker, remove it after rinsing with distilled water into the 
beaker, and transfer the solution to a 500-cc. flask, washing out 
all FeCl, from beaker. Make up to mark with distilled water. 
Concentrate a 100-cc. aliquot portion and reduce with SnCl.. 
Stir constantly, adding the material, drop by drop, from a 
burette until apple-green color is produced—from chrome- 
oxidized blues. For chlorate-oxidized blues, the SnCl, is added 


* Parry and Coste, The Analyst, Vol. 21, pp. 225 to 230 (1896). 


364 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


until complete disappearance of the yellow color. At once pour 
in 50 ce. cold HgCl, and 50 ec. MnSO,, dilute with cold distilled 
water to about 600 cc. and titrate with KMnO,. For those in- 
terested in this method, see files of Drugs, Oils and Paints. 


ANALYSIS OF ULTRAMARINE BLUE 


An analysis is of little value for determining the quality of 
pure ultramarines, but is useful in the identification of foreign 
admixtures. Practical tests as to the stability and compatibil- 
ity of the pigment in mixtures with other pigments, coloring 
power, tint, fineness, fastness to light, etc., are more important 
than chemical analysis. 

Moisture.—Heat 2 g. of the pigment at 105° C. for two hours, 
cool and weigh. The loss in weight is reported as moisture. 

Silica.—Treat 1 g. of the pigment in a covered dish or cas- 
serole with 30 cc. of HCl (1:1), heat until decomposed, wash 
off and remove cover, and evaporate to dryness on the steam- 
bath. Moisten with concentrated HCl and again evaporate to 
dryness, add 1 to 2 cc. of concentrated HCl, let stand about 5 
minutes, add hot water, filter and wash the insoluble matter 
with hot water. If great accuracy is desired, evaporate the 
filtrate to dryness, take up with HCl and water, filter on a 
second paper, wash, and add the residue to the main insoluble. 
Ignite the insoluble matter, cool and weigh. Determine SiO, by 
volatilization with H,SO, and HF. Make a qualitative examina- 
tion of any residue that may remain. 

Alumina.—Render the filtrate from the silica faintly alkaline 
with NH,OH, boil a few minutes, filter, wash with hot 2-per- 
cent NH,Cl solution, ignite and weigh as Al,O,( + Fe,0,). For 
more accurate work, dissolve the Al(OH), precipitate in HCl 
and reprecipitate as above. 

Sodium Oxide—Acidify the filtrate from the Al,O, with 
H.SO,, evaporate to dryness, ignite (finally adding solid am- 
monium carbonate) and weigh as Na,SO,. Calculate to Na,O. 
If calcium is present it should be precipitated with ammonium 
oxalate in the filtrate from the Al,O,, ignited and weighed as 
CaO, and the sodium determined in the filtrate from the calcium 
oxalate, as described. . 

Total Sulfur.—Mix 1 g. of the ultramarine with 4 FOOL 
Na,CO, and 4 g. of Na,O, in a nickel crucible, cover with about 1 


BLUE PIGMENTS 365 


g. of Na,CO, and fuse, using an aluminum or asbestos shield 
to prevent the sulfur being taken up from the gas. Dissolve 
the fused mass in dilute HCl, filter and wash, if necessary (there 
should be no insoluble residue), precipitate with BaCl, and de- 
termine total sulfur by weighing as BaSO,. Calculate to S. 

Sulfur Present as Sulfate——Dissolve 1 g. of the pigment in 
dilute HCl, boil to expel H.S, and filter if necessary; make the 
solution faintly alkaline, with NH,OH and just distinctly acid 
with HCl, and treat with BaCl, in the usual manner. Calculate 
BaSO, to SO, and to S. 

Sulfur Present as Sulfide-—Subtract the sulfur present as 
sulfate from the total sulfur. 


ANALYSIS OF COBALT BLUE 


This pigment is essentially a compound of the oxides of alum- 
inum and cobalt.* Certain shades of ultramarine blues are often 
sold under the name “cobalt blue.” 

Moisture.—Heat 2 g. of the pigment at 105° C. for 2 hours. 
The loss in weight is reported as moisture. 

Alumina.—Fuse 1 g. of the pigment with 12 to 15 g. of sodium 
or potassium pyrosulfate cool, digest with water and HCl, filter, 
and wash the residue with hot water. Make the filtrate up 
to 250 cc. in a graduated flask and mix. Ignite the residue, 
cool, weigh, and examine for SiO, and BaSO,. Dilute an aliquot 
portion of the filtrate to 200 cc., add 5 g. of NH,Cl, heat to boil- 
ing, and add dilute NH,OH till just distinctly alkaline (a few 
drops of 0.2-per-cent alcoholic solution of methyl red is recom- 
mended as indicator). Boil for one or two minutes, filter at 
once, dissolve the precipitate with HCl, and reprecipitate as 
before. Filter, wash thoroughly with hot 2-per-cent NH,Cl 
(or NH,NO,) solution, ignite, and weigh as AI,O.,. 

Calcium and Magnesium.—Unite the filtrates from the AI,O,, 
saturate with hydrogen sulfide, filter, and determine calcium and 
magnesium in the filtrate in the usual manner. 

Cobalt Oxides.—Subtract the determined constituents from 
100 and report the difference as cobalt oxides, unless a qualita- 
tive examination shows the presence of other substances in sig- 
nificant amounts. Should the pigment contain phosphoric acid 
(or arsenic acid) in more than negligible amounts, these must 


* “ Analysis of Paint and Varnish Products,” C. D. Holley, p. 210 (1912). 


366 EXAMINATION OF PAINTS, VARNISHES AND COLORS 


be removed before determining aluminum, calcium and mag- 
nesium.t 


ANALYSIS OF SUBLIMED BLUE LEADT 
BASIC SULPHATE—BLUE LEAD 


Total Lead.—The total lead content is determined by the vol- 
umetric method for lead as outlined under Basic Sulphate-White 
Lead. 

Total Sulphur.—Treat 0.5 gram with 10 cc. of water and a 
few ec. of bromine water. Boil gently until all the bromine has 
passed off. Dilute with water, add another portion of bromine 
water, boil, and continue the treatment until the sediment has 
become white in color. Add 8 cc. of nitric acid, evaporate until 
the brown fumes of nitric acid have disappeared, dilute with 
water and add an excess of sodium carbonate. Determine as 
outlined under Basic Sulphate-White Lead. 

Lead Sulphate-—On a separate sample determine the lead 
sulphate as outlined under Sublimed White Lead, by transposi- 
tion of the sulphate with sodium carbonate. 

Lead Sulphite.—Boil one and one-half: grams of the sample 
with 3 grams of sodium carbonate, allow to stand, filter and 
thoroughly wash. To the filtrate add 3 cc. of bromine water, 
heat gently to oxidize the sodium sulphite to sulphate, acidify 
with HCl and precipitate the sulphate with barium chloride. 
Filter, wash and weigh in the usual manner. The barium sul- 
phate formed will contain both the sulphur present as sulphate 
and that present as sulphite converted to sulphate. Deduct the 
amount present as sulphate and calculate the remainder to lead 
sulphite. 

Lead Sulphide.—Deduct the sulphur present as sulphate and 
sulphite from the total sulphur and report the difference as lead 
sulphide. 

Lead Carbonate.—A small amount of lead may be present as 
carbonate. Determine the carbonic acid present as outlined 
under Basic Carbonate White Lead, and calculate this carbonic 
acid to lead carbonate. 

Lead Oxide.—Deduct the lead present as lead sulphate, lead 
ae tee } sNora ieiay eee of Chemical Analysis,” Lunge-Keane, Vol. III, 


t “The Chemical Analysis of Lead and its Compo . 
White, pp. 22-24, mpounds,” Schaeffer and 


BLUE PIGMENTS 367 


sulphite, lead sulphide and lead carbonate from the total lead 
and report the difference as lead oxide. 

Zine Oxide—Determine the zine present as outlined under 
Sublimed White Lead, and report it as Zine Oxide. 

Carbon and Volatile Matter—lIgnite the sample in a partially 
covered crucible at a low heat for two hours. Report the differ- 
ence as carbon and volatile matter. 


CHAPTER XLII. 


ANALYSIS OF GREEN PIGMENTS 
(CHROME GREEN) 


A pure chrome green should contain only Prussian blue and 
pure chrome yellow. A microscopic examination should be made 
to determine whether the green is a combined precipitation 
product, which is of the greater value, or one mixed after sep- 
arate precipitation. A good green will show the presence of 
green and blue particles, while a poor green will show yellow 
and blue particles mixed with green. . 

Moisture.—Heat 2 g. of the pigment at 105° C. for two hours. 
The loss in weight is reported as moisture. 

Insoluble Matter.—Heat gently 1 g. of the pigment in a small 
porcelain dish until the blue color has been decomposed. The 
heating should be carried out very carefully so as not to render 
the iron difficultly soluble. (With some very pure chrome greens 
it may be advantageous to mix the sample with 2 to 5 times its 
weight of pure barium sulfate or pure anhydrous sodium car- 
bonate before igniting.) Let cool, transfer to a beaker, and de- 
termine insoluble matter as outlined in Section 5 for Yellow 
Pigments. 

Lead.—Determine lead in the filtrate from the above as out- 
lined in Section 6 for Yellow Pigments. 

Iron, Alumina and Chromium.—Determine iron, aluminum > 
and chromium in the filtrate from the PbS as outlined for Yel- 
low Pigments, making a double precipitation. 

Zinc, Calcium, and Magnesium.—Determine zinc, calcium and 
magnesium in the filtrate from the iron, aluminum and chrom- 
ium determination as outlined for Yellow Pigments. 

Carbon Dioxide.——Determine carbon dioxide by the evolution 
method, using dilute HNO, (1:5). 

Sulfuric Anhydride.—Heat gently 1 g. of the pigment, cool, 
transfer to a beaker, add 30 ce. of concentrated HCl, cover, and 
heat on a steam-bath for about 30 minutes (in some cases, the 
iron compounds will go into solution more readily by letting the 
solution stand for some time at room temperature and then heat- 
ing). Wash off cover, add 50 cc. of boiling water, boil for five 


368 


GREEN PIGMENTS 369 


minutes, filter, render the filtrate faintly alkaline with NH,OH, 
then slightly acid with HCl, heat to boiling, and precipitate with 
BaCl, (15 cc. of 10-per-cent solution) in the usual manner, boil- 
ing about ten minutes. Filter, wash with hot water, ignite, and 
weigh the BaSO,,. 

Nitrogen.—Determine nitrogen on a l-g. portion of the pig- 
ment by the Kjeldahl-Gunning Method, digesting for at least 
214 hours. 

Water-Soluble Matter.—Weigh 2.5 g. of the pigment into a 
graduated 250-cc. flask, add 100 ec. of water, and boil for five 
minutes. Dilute with water, let stand until at room tempera- 
ture, make up to the mark, mix, and let settle. Filter through 
dry paper and discard the first 25 ec. Transfer 100 cc. of the 
clear filtrate to a weighed dish, evaporate to dryness on a steam- 
bath, dry in an oven at 105° C. for 30 minutes, cool and weigh. 


CHAPTER XLIII. 


ANALYSIS OF BLACK PIGMENTS 


The black pigments include those which contain carbon as 
their essential constituent. The introduction of asphaltic and 
coal-tar mixtures complicates their chemical analysis. For those 
pigments which contain coal-tar mixtures, recourse may be had 
to works* covering this matter thoroughly. 

The analysis of the simple black pigments may be carried out 
in the following way: 

Moisture.—Dry 2 grams at 105° C. for two hours. 

Oil.— Extract 2 grams, with ether in a fat-extraction ap- 
paratus. 

Carbon.—Determine the carbon by difference after determin- 
ing the moisture, oil and ash. For an exact determination of 
carbon make a combustion test, absorbing the carbon dioxide in 
soda-lime or caustic potash as usual. 

Ash.—Ignite 2 grams to a bright red heat until all the carbon 
is driven off. If graphite is present, the ignition should be car- 
ried out with the aid of oxygen. Should carbonate be present, 
mix the ash with a small amount of ammonium carbonate and 
again ignite, thus reconverting to carbonate any oxide which 
may have been formed. 

Analysis of Ash.—The ash is boiled with concentrated HCl 
and the insoluble residue determined in the usual manner. The 
filtrate is examined for calcium, magnesium and phosphoric acid. 

Calculate the magnesium to phosphate, any residual phos- 
phoric acid to calcium phosphate and any residual calcium to 
carbonate. 

Gases.—Black pigments such as lamp or gas blacks may con- 
tain as high as 15 per cent absorbed or adsorbed gases. High 
vacuum is necessary to free such gases from the pigment. 


* Allen’s “Commercial Organic Analysis,” 4th Edition; “The Analysis of 
Paints,” Gardner and Schaeffer. 


370 


INDEX 


A 


Accelerated roof expusure tests, 197 
Accelerated testing cabinets, 71 
Accelerated testing vs. exterior ex- 
posure, 76 
Accelerated weathering test chart, 
74 
Acetone in lacquer, 287 
Acid number of varnishes, 246 
Acid resins, 262 
Acid test, 279 
Acidity, Effect of on light resist- 
ance, 123 
Acidity of lacquers, 285 
Air-liquid tension, 155 
Alkali resistance test, 279 
Aluminwm oxide in aluminum stear- 
ate, 190 
Aluminum stearate, 181 
Aluminum stearate solutions, 186 
American Society for Testing Ma- 
terials tests on insulating 
varnishes, 276 
American Society for Testing Ma- 
terials tests on shellac, 267 
American vermilion, 358 
Analysis of aluminum stearate, 191 
bituminous paints, 296 
driers, 255 
paints, 213 
- paint oils, 218 
paint vehicles, 213 
pyroxylin coatings, 283 
resins, 258 
white paint, 304 et seq. 
Anthraquinone tests, 302 
Antifouling paints, 208, 204, 354 
Antimony oxide, 304, 327 
Apparatus for oil absorption, 108 
specific gravity, 84 
testing shellac, 275 
Abestine analysis, 327 
Ash in varnishes, 246 
Asphalts, 301 
Asphalt tests, 301 


B 


Barium carbonate, 304 
Barytes analysis, 329 
Basic chromate yellows, Analysis of, 
358 
Bending test of films, 13 
Benzol, 289 
Benzol in paints, 217 
Bituminous cement, 293 
japans, 295 
paints, 293 
Analysis of, 296 
varnish, 293 
Black pigments, 370 
Blanc fixe analysis, 329 
Bleached shellac, 272 
Blue pigments, 362 
Blown oil test on thinners, 178 
Boiled linseed oil, Constants of, 219 
Bone dry shellac, 272 
Brightness and hiding power of pig- © 
ments, 28, 24, 28 
Brightness of white pigments, 210 
Bulking values of 
colors, 89 
paint liquids, 88 
pigments, 89 


C 


Cadmium lithopone, 360 
Calcium pigments, Analysis of, 328 
Calculating analysis of lead pig- 
ments, 315 
Camphor in lacquer, 289 
Candlenut oil constants, 219 
Caramel solutions, Color strength of, 
166 
Carbon dioxide apparatus, 307 
Catfish oil constants, 220 
Celluloid in varnish, 254 
Cellulose acetate in varnish, 254 
nitrate in varnish, 254 
stability, 292 


371 


372 


INDEX 


Te ———ee—e_e—_e_—_—_—eeeeeeee 


Chemical examination of aluminum 
stearate, 188 
Chia oil constants, 219 
Channel catfish oil constants, 219 
China clay analysis, 327 
Chinese blue, 362 
Chinese wood oil analysis, 239 
in paints, 217 
specifications, 239 
constants, 219 
Chrome green, 368 
yellows, 358 
Coal tar pitch, 302 
Coating apparatus, Experimental, 13 
Cobalt blue, 365 
drier, 255 
Coefficient of diffuse reflection of 
pigments, 80 
Color analyzer, Keuffel & Esser, 42 
change cabinet, 61 
chip maintenance, 45 
of varnishes, 167 
white pigments, 210 
standards for varnishes, 165 
strength of caramel solutions, 166 
systems, 34, 35 
Colorgraphing color, 43 
Colorimeter for white 
Pfund, 21, 22 
Colorimeters, 34, 36, 38 
Colorimetric determination of cop- 
per, 336 
Colors, Method for testing, 206 
Colors, Wave length of, 46, 47 
Condition of pigments on absorbing 
oil, 117 
Consistency of stearate 
184 
Constants of oils, 219, 220 
Cooper-Hewitt ultraviolet light, 125 
Copper oxide in paint, 354 
paint, 354 
Corroded white lead, 304 
Corn oil constants, 219 
Cottonseed oil constants, 219 
Cumaron resin, 266 
Cryptometer, Pfund, 19, 20 
Cyanide blue, 362 


D 


Detection of special oils in paints, 
216 
spirit varnish components, 252 


surfaces, 


solutions, 


Diazo reaction, 303 
Dielectric strength tests, 277 
Diffuse reflection of pigments, Co- 
efficient of, 80 
Discoloration of interior whites, 61 
Distillation range of mineral spirits, 
179 
Distillation range of thinners, 171 
Draft test apparatus, 247 
Draft test on varnish, 247 
Drier analysis, 255 
Driers in 
paints, 216 
varnishes and pigmented enamels, 
256 
Drying time meter, 56 
Du Nouy surface tension apparatus, 


156 
E 
Eastlack-Booge test for lithopone, 
134 


Eastman Universal Colorimeter, 38 


Effect of acidity on light resistance, — 


123 
Effect of colors on hiding power, 26 
Effect of 
lacquer upon metal, 285 
solvents upon resins, 259, 260 
ultraviolet light on pigments, 146 
Elasticity of paint films, 17 
Ester gum, 265 
Evaporation effects, 169 
Evaporation speed of lacquer sol- 
vents, 291 
Experimental coating apparatus, 138 
Exposure tests on 
antifouling paints, 203, 204 
metal paints, 195 
paints and varnishes, 193, 199 
paper, 12 
Exterior exposure vs. accelerated 
testing, 76 


F 


Figuring bulking values of paint, 90 
Film gauge, Pfund, 27 
Films, Elasticity of, 17 

Hardness of, 68 

Hiding power of, 17 

Nelson tests on, 17 

paint, Testing of, 11 


; 
s 
E 


Pet OR Se ee ga ee eee ee ee Yee 


INDEX 


373 


Films, 
strength of, 14-16 
tested for hardness, Photomicro- 
graphs of, 69 
thickness of, 14-16 
Use of microscope for examining, 
64 
Fineness, Greene method for determ- 
ining, 101 
of paint pigments,. 91 
testing apparatus, 95, 96 
Fish oil 
constants, 220 
in paints, 217 
Fixed oils and resins in varnish, 248 
Flake red lead analysis, 343 
Flash point of varnishes, 246 
Flaxseed analysis, 237 
examination, 237 
Flow curves of paints and varnishes, 
51 
Flowing values of paints and var- 
nishes, 54, 55 
Flowmeter, 48 
Fossil resin analysis, 258 
Fur seal oil constants, 220 
Fusibility of resins, 261 


G 


Gardner photomicrographic camera 
for exterior tests, 106 
Gardner-Holdt colorimeter, 165 
viscometer, 150 
Gas resistance of varnishes, 247 
test apparatus, 247 
Gel test apparatus for 
stearate, 185 
Gels of aluminum stearate, 189 
Grapeseed oil constants, 219 
Graphic analysis of sublimed white 
lead, 315 
Grayfish oil constants, 220 
Green pigments, 368 
Greene method for determining fine- 
ness, 101 
Gypsum, 304 


aluminum 


H 


Hardness of films, 68 
Heat test, 279 
Heat test for tung oil, 240 


Heating test on tung oil, 244 
Heavy bodied linseed oil, Constants 
of, 219 
Hempseed oil constants, 219 
Hexabromide numbers on oils, 234- 
236 
Hexabromide test on oils, 224 
Hiding power, 
Effect of colors on, 26 
of films, 17, 21 
of pigment-oil mixtures, 27 
of pigments, 28, 25 
tests, Shaded paper for, 18 
Humidity cabinet for testing films, 
59 


Indian red, 351 
Insulating varnishes, 276 
Interfacial tension, 154 
apparatus, 158 
Iron arc 
equipment design, 135 
test on lithopone, 134, 138-142 
Iron cyanide blues, 362 


J 


Japanese wood oil constants, 219 


K 


Kapok seed oil constants, 219 

Kauri gum reduction tests on min- 
eral spirits, 177 

Keuffel & Esser color analyzer, 42 


L 


Lacquer analysis, 293 
Lacquer components, 292 
Lake colors, Qualitative tests for, 
347 
Lead chromate, 358 
drier, 255 
oxide analysis, 333 
Leaded zinc, 304, 316 
Light resistance of lithopone, 128 
Linseed oil 
analysis, 218 
constants, 219 
Litharge analysis, 336 
Lithographic linseed oil, Constants 
OFA219 


at4 


INDEX 


Litho] red, Analysis of, 348 
Lithopone, 304 

analysis, 321, 360 

Light resistance of, 123 

tests for darkening, 142 
Lumbang oil constants, 219 


M 


Manganese drier, 255 
Marine exposure tests, 204 
Mcllhenny-Steele method on shellac, 
273 
Melting point of resins, 261 
Menhaden oil constants, 220 
Mercury arc tests on pigments, 80 
Method of determining texture of 
pigments, 119 
Microscope, Use of, for examining 
films, 64 
Mineral spirits, Distillation range of, 
179 
Sulphur test on, 179 
Testing, 175 
Moist cabinet for testing paints, 58 
Moisture in shellac, 271 
Mullen’s tester, 10 


N 


Nelson cabinet, 71 
test on paint films, 17 
New Jersey Zinc Company’s accele- 
rated testing cabinet, 72 
Non-volatile matter, 281 


O 


Ochre analysis, 355 
Oil absorption 
of colors, 207, 208 
factors on pigments, 110 
of pigments, 107, 111 
Oil analysis, 218 et seq. 
constants, 219, 220 
in flaxseed cake, 237 
test, 280 
Opacity of pigments to ultraviolet 
light, 147 
Optical dispersion of tung oil, 245 
Orange mineral analysis, 339 
pigments, 358 


Organic color in red lead, 344 
lakes, 847 
red pigments, 347 

Oticia oil constants, 219 


iM 


Palo Maria oil constants, 219 
Panels for exposure tests, 194 
Paper, Tests on, 12 
Para red, 347 
Peanut oil constants, 219 
Perilla oil constants, 219 
Permeability of films, 10 
Pfund paint testing instruments, 19- 
22,21, 29, 308 
Photographing pigments, 102 
Photographs of exposed lacquers, 
varnishes and paints, 202 
Photomicrographic camera for ex- 
terior tests, Gardner, 106 
Photomicrographs of films tested for 
hardness, 69 
of paint texture, 121 
of paint and varnish films, 65-67 
of pigments, 98-100, 102, 104, 105 
of pigment screens, 92 
of pigment texture, 121 
Physical character of films, 9 
Examination of paint materials, 9 
properties of white pigments, 210 
Pig lead analysis, 336 
Pigment in lacquer, 285 
Plasticity of paints and varnishes, 
51, 55 
Plasticity and yield value, 48 
Polymerized oils and resins, 249 
Poppyseed oil constants, 219 
Prince’s metallic red analysis, 351 
Protein in oil cake, 288 
Prussian blue, 362 
Pycnometer for specific gravity, 86 
Pyroxylin lacquer coatings, 283 


Q 


Quality test on tung oil, 244 
Quartz tube mercury lamp, 73 


R 


Raisinseed oil constants, 219 
Raw Linseed oil, Constants of, 219 


ee ee ee ee ae ee ee ee 


_—— P , ‘ 
ill ee tet 


a 


ee ee ee oe 


INDEX 


Red lead analysis, 333, 339 
oxide of iron analysis, 351 
Reporting conditions on exposure 
tests, 196 
Resinates in paints, 216 
Resin acids, 262 
Resin analysis, 258, 266 
Solubility of, 259, 260 
in varnish, 248 
Rosin, 265 
in shellac, 269, 273 
oil constants, 219 
Routine testing methods for white 
pigments, 210 
Rubberseed oil constants, 219 


S 


Salmon oil constants, 220 
Saponification value of lacquers, 288 
Sardine oil constants, 220 
Schaeffer analytical methods, 348 
Seal oil constants, 220 
Sesame oil constants, 219 
Settling test for pigments, 211 
Shaded paper for hiding power 
tests, 18 
Shark oil constants, 220 
liver oil constants, 220 
Shellac purity by Steele-McIlhenny 
method, 273 
Shellac testing, 267 
weighing, 275 
Ship paints, 204 
Sienna analysis, 355 
Silica analysis, 327 
Skate liver oil constants, 220 
Soft lumbang oil constants, 219 
Softening point of resins, 261 
Solids in lacquer, 286 
Solubility of resins, 261 
Solutions for shellac testing, 268 
Solutions for testing oils, 218 
Solvent in varnishes, 246 
Source of ultraviolet energy, 78 
Soya bean constants, 219 
Special oils in paints, Detection of, 
216 
Specific gravity 
apparatus, 82, 84 
of colors, 89 
of paint liquids, 85, 88 
of pigments, 81, 89 
Speed of evaporation of thinners, 
169 


375 


Spectrophotometers, 34, 40 

Spirit varnishes, 352 

Spreading rate of paints, 32, 33 

Standard solutions for testing oils, 
218 

Stearate solutions, 183 

Steel panel exposure tests, 195 

Steele-McIlhenny method on shellac, 
273 

Steele & Washburn test, 225 

Strength of films, 14-16 

Sublimed blue lead analysis, 366 

Sublimed white lead, 304, 310 

Sulphur test on mineral spirits, 179 

Sunflower oil constants, 219 

Surface tension, 154 

of paint oils and liquids, 157 
Synthetic resin, 265, 266 


Ak 


Talking machine record tests on pig- 
ments, 98-100 
Tar pitch, Coal, 301 
water gas, 302 
wood, 302 
Tension of paint liquids, 160 
Testing cabinets, 71 et seq. 
Testing colors for tone and strength, 
206 
Testing paint films, 11 
Testing the light resistance of litho- 
pone, 124 
Texture of pigments, 118 
Thickness of films, 14-16, 30, 31, 33 
Thinners, Blown oil test on, 178 
Distillation range of, 171 
Effect of upon viscosity, 174 
Evaporative rate of, 173 
Viscosity effects induced by, 169 
Tinting strength of white pigments, 
ra 
Titanium oxide, 304 
Titanox analysis, 324 
paint analysis, 326 
Toluidine red, 348 
Total solids in lacquer, 286 
Tricresyl phosphate, 289 
Tuna fish oil constants, 220 
Tung oil constants, 219 
test apparatus, 240 
testing, 239 
Turpentine, 175 
Tuscan red analysis, 351 


376 


U 


Ultramarine blue, 364 


Ultraviolet energy, Source of, 78 
light for testing cabinet, 73 
opacity tests, 147, 148 
tests on pigments, 146 

Umber analysis, 355 

Use of microscope for examining 
films, 64 

Uviare lamp, 125 
test on lithophone, 126-134 


V 


Varnish analysis, 246 
Varnishes, Color of, 167 
Viscosity of, 174 
Vehicles, Analysis of, 213 
Venetian red analysis, 355 
Vermilion analysis, 347, 358 
Viscosity, Effect of different thin- 
ners on, 174 
effects induced by thinners, 169 
of stearates, 184 
varnishes, 149, 174, 284 
in poises, 151 
Volatile constituents in lacquer, 287 


Volatiles in paints and varnishes, 
216, 248 


INDEX 


W 


Washburn and Steele test, 225 
Water absorption tests, 279 
gas tar, 302 
in oil cake, 237 
Wave length measurements on pig- 
ments, 80 
of colors, 46, 47 
pigments, 41 
Whale oil constants, 220 
White lead, 304 
White paint analysis, 304 et seq. 
White pigments, Brightness of, 210 
Color of, 210 
Physical properties of, 210 
Routine testing methods for, 210 
Tinting strength of, 211 
Whiting analysis, 328 
Wood oil constasts, 219 
Wood tar, 302 
Y 


Yellow lithopone, 360 
pigments, 358 
Yellowing of whites, 61 
Yellow tailfish oil constants, 220 
Yield of paint, 90 
Yield values, 48 
Z 


Zine lead, 304 
oxide, 304 
analysis, 317 


STANDARD SPECIFICATIONS 


For USE OF DEPARTMENTS AND INDEPENDENT ESTABLISHMENTS 
OF THE U. S. GOVERNMENT 
OFFICIALLY ADOPTED BY THE 
FEDERAL SPECIFICATIONS BOARD 
The specifications issued to date, in so far as they are available at 
the Government Printing Office, have been bound in this volume. 
The list is given below: 
Bureau 


ards ___ fications 
er Board Edition Title 


° 0) 
82 4 2nd Edition—Linseed Oil. 
84 5 29nd Edition—Basic Carbonate White Lead. 
85 6 2nd Edition—Basic Sulphate White Lead. 
86 c 2nd Edition—Turpentine. 
87 8 2nd Edition—Zine Oxide. 
] 


2nd Edition—Leaded Zine Oxide. 
89 10 2nd Edition—White and Tinted Paints (Exterior). 
90 11 2nd Edition—Red Lead. 
91 12 2nd Ediiton—Ocher. 
93 13 2nd Edition—Iron Oxide Paints. 
94 14 2nd Edition—Black Paint. 
97 15 3rd Edition—Green Paint. 
98 16 2nd Edition—Mineral Spirits. 
102 17 Ist Edition, corrected—Composite Thinner. 
103 18 3rd Edition—Spar Varnish 
104 19 9nd Edition—Asphalt Varnish. 
105 20 29nd EKdition—Liquid Paint Drier. 
111 21 2nd Edition—Flat Interior Lithopone Paint. 
117 22 2nd Edition—Interior Varnish. 
146 66 Sept., 1923—Water-Resisting Red Enamel. 
147 67 Sept., 1923—Gloss Interior Lithopone Paint. 
163 115 Feb., 1924—Titanium Pigment, Dry and Paste. 


At a recent meeting of the Federal Specifications Board, two new 
specifications were adopted and will be printed in the very near fu- 
ture. Copies may possibly be obtained about the first of April, 1925, 
from the Government Printing Office, Washington, D. C., at five 
cents each. These specifications will be designated as follows: 


“Federal 
Bureau Specifi- 
of cations 
Stand- Board 
ards Spectfica- 
Circular cation Title 
No. 0. k : 
DOO re a Specification for Heavy Rust Preventive Com- 


pound. 
Rr eae Nitanox-Zine Exterior Paint. 


February 1, 1925. 


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DEPARTMENT OF COMMERCE 


BUREAU OF STANDARDS 
S. W. STRATTON, Direcior 


CIRCULAR OF THE BUREAU OF STANDARDS 
No. 82 


[2d edition. Issued June 8, 1922] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
LINSEED OIL, RAW, REFINED, AND BOILED 


ee ee 


FEDERAL SPECIFICATIONS BOARD 
STANDARD SPECIFICATION No. 4 


This Specification was officially adopted by the Federal Specifications Board, 
on February 3, 1922, for the use of the Departments and Independent Establish- 
ments of the Government in the purchase of materials covered by it. 


CONTENTS 


rg 
» 
09 
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(TS oe ee a irre ene ee Oa 
PEE ER ITIOAIOD oe. preeeiee y <P TTD\eT eee 
Se OS ici inate ea aren Se ee CR 
Bea i a ii ey nie args eu gg ys pee pe 


1. GENERAL 


Linseed oil, raw, refined, or boiled, as specified in contract, shall 
be pure and shall conform to the following requirements: 


° 


OW COBRW NHN HH 


MR WN 


RAW LINSEED OIL 


Maximum Minimum 
Loss on heating at 105 to 110° C (per cent).........---.--- 0; 2a a Aes ee 
Foots by volume (per cent).......-.-.-------------------- rt eg Pee 
Specific'gravity 15.5/15.5° C...........-------------++---- . 936 0. 932 
MMII he oe. Fee oe pn Os ea bs Se ee Ein. Ge a ee ae 
Saponification mumber........--.---.----------+-++++--- 195. 0 1@9. 0 
Unsaponifiable matter (per cent).-..-..------------------ Eee Ree aie 
Iodine number (Hanus) @..........-...-------+-----+--+-0-[---2 ee ee ere? 170. 0 
Colog. cai hiss yey ~ + Pe RORY Se CER Apes, Sym Mee ee Fe" Wot darker than a freshly 
prepared solution of 1.0 
g potassium bichromate 


in 100 cc pure strong 
(1.84 specific gravity) 
sulphuric acid. 


a@ When raw linseed oil from North American seed is specified by the purchaser, the iodine number 
must be not less than 180 and the oil shall conform to all the other requirements as above. 


109795°—22 


2 , Curcular of the Bureau of Standards 


REFINED LINSEED OIL 


Contract shall state whether acid refined or alkali refined is 
desired. 


Loss on heating at 105 to 110° C (per cent)................. 0,27 | et EAL 
Foots by volume,(per cent)... . «ssa: ne gsy cy. - 9h ee oe RA AM ack sows 
specific gravity. at 15.5/1S.5°400..0...02 3.0)... ae . 936 0. 932 
Acid number (acid refined oil)........................-..- 9.0 3.0 
Acid number (alkali refined oil).......................... 3.0: ieee 
saponification number. .2.¢7. 202. {Tt ee 195.0 | 189.0 
Unsaponifiable matter (per cent)....................-...- Li Sosa. 8 Ub kscs 
Iodine number (Hants) @ 2.4. sicewes sve 1. nt A. Sea ee 170.0 
Color. ........-35 gah beeen arg aes Sree Not darker than a freshly 
prepared solution of 0.1 
g potassium bichromate 


“. 100 cc Bs stron: 
1.84 specific gravity 
Serie tele = acid. 


a When refined linseed oil from North American seed is specified by the purchaser, the iodine number 
must be not less than 180 and the oil shal! conform to all the other requirements as above. 


BOILED LINSEED OIL 
Boiled oil shall be pure, well-settled linseed oil that has been 


boiled with oxides of manganese and lead. It shall conform to 
the following requirements: | 


Loss on heating at 105 to 110° C (per cent)................. O. 2 ee a nee 
Specific gravity-at 15.5/15.5° Cli3i 2). , 1h ee 945 0. 937 
Acid number. ccs oi pss neine ee tee eee 8.6 Ve 
Saponification number... ......, 2. J....-.-5 dacs pene 195. 0 189.0 
Unsaponifiable matter (per cent)......................-.. 1.30 Scouse = 
Iodine number (Hanus) 4... 2.2.0.5)... 05.2 os. 11s eh 168. 0 
Asher cent). . 2.0 0 Se -t =f ol 
Manganese (per cent)........2.:)..22. 001.1. 02. ee | YS OS 
Léad (per cent)... 625.02. 55 6 ee ee 27 eae 1 
Time of drying on glass (hours)...............//...22.....) \ 20: phe 


eS te 
@ When boiled linseed oil from North American seed is specified by the purchaser, the iodine number 
must be not less than 178 and the oil shall conform to all the other requirements as above. 


Linseed Ou 3 


2. SAMPLING 


_ The method of sampling given under (a) below should be used 
whenever it is feasible to apply it. To meet conditions when (a) 
is not applicable, method (6), (c), or (d) is to be used, according to. 
the special conditions that obtain. 

(a) DuriInGc LoaDING oF TANK Cars OR FILLING OF CONTAINERS 
FOR SHIPMENT AT THE Factory.—The purchaser’s inspector shall 
draw a sample at the discharge pipe where it enters the receiving 
vessel or vessels. The total sample shall be not less than 5 gallons 
and shall be a composite of small samples of not more than 1 
pint each taken at regular intervals during the entire period of 
loading or filling. 

The sample thus obtained shall be thoroughly mixed, and from 
this composite sample three portions of not less than 1 quart each 
shall be placed in clean dry glass bottles or tin cans which must 
be filled with the sample and securely stoppered with new clean 
corks or well-fitting metal covers or caps. ‘These shall be sealed 
and labeled distinctly by the inspector, and one delivered to the 
buyer, one to the seller, and the third held for check in case of 
dispute. | 

(6) From LoapED TANK CARS OR OTHER LARGE VESSELS.—The 
total sample shall be not less than 5 gallons and shall be a com- 
posite of numerous small samples of not more than 1 pint each 
taken from the top, bottom, and intermediate points by means of 
a glass or metal container with removable stopper or top. This 
device attached to a suitable pole is lowered to the various de- 
sired depths when the stopper or top is removed and the con- 
tainer allowed to fill. The sample thus obtained is handled as 
in (a). . 

(c) BARRELS AND Drums.—Not less than 5 per cent of the pack- 


ages in any shipment or delivery of barrels and drums shall be 


sampled. ‘The packages shall be shaken, rolled, and stirred to 
thoroughly mix the contents. The samples from the individual 
containers shall be taken through the bung hole or holes not less 
than 114 inch in diameter bored in the head or side for the pur- 
pose. The apparatus for drawing the sample shall consist of a 
glass tube about 1 inch in diameter and somewhat longer than the 
length or diameter of the oil container, a conical stopper that will 
fit the glass tube and is not more than ™% inch long fastened to a 
stiff metal rod not more than 14 inch in diameter and not less than 
4 inches longer than the glass tube. The stopper is lowered by 


4 Circular of the Bureau of Standards 


the rod until it rests on the bottom of the cask, the tube slipped 
down slowly over the rod, and finally pressed on the stopper. By 
holding tube and rod the column of oil can then be removed. ‘This 
process is repeated until the required amount of sample is obtained, 
which must be not less than 2 gallons. ‘This is mixed and handled 
as in (a) ; 

(qd) SMALL CONTAINERS, CANS, ETC., OF 10 GALLONS OR 
Less.—Small containers, cans, etc., of 10 gallons or less should 
be sampled while filling by method (a) whenever possible. When 
method (a) is not applicable, it is mutually agreed that: In all 
cases the total sample taken shall not be less than 3 quarts. 
This shall be obtained by taking at least one package from each 
lot of not more than 300 packages. The sample thus taken shall 
be Sheu ee mixed and subdivided as in (a). 


3. LABORATORY EXAMINATION 


Samples shall, in general, be tested by the following methods, 
but the purchaser reserves the right to apply any additional tests 
such as specific tests for foreign oils, rosin, etc., or use any avail- 
able information to ascertain whether the material meets the 
specification. The laboratory sample shall be thoroughly mixed 
by shaking, stirring, or pouring from one vessel to another and 
the samples for the individual tests taken from this theropealy 
mixed sample. 

(a) Loss on Heatinc at 105 To 110° C.—Place 10 g of the 
oil in an accurately weighed 200 cc Erlenmeyer flask; weigh. 
Heat in an oven at a temperature between 105 and ir0°C€ for 30 
minutes; cool and weigh. Calculate the percentage loss. This 
deccrniacien shall be made in a current of dry carbon dioxide 
gas. | 

(b) Foots.—With all materials at a temperature hepineee 20 
and 27° C mix, by shaking i in a stoppered flask for exactly one 
minute, 25 cc of the well-shaken sample of oil, 25 cc of acetone 
(see 4(a)) and 10 ce of the acid calcium chloride solution (see 
4(b)). Transfer the mixture to a burette where settling can take 
place for 24 hours. The temperature during this period should 
be, between..20 and 27°C, 

The volume of the stratum lying between the olehe pr 
chloride solution and the clear acetone and oil mixture is read 
in tenths of a cubic centimeter ora fraction thereof ‘This reading 
multiplied by four expresses the amount of foots. present as 
percentage by volume of the oil taken. 


Pe ee ee 


Linseed Oil 5 


(c) SpeciFIc Gravity.—Use a pyknometer accurately stand- 
ardized and having a capacity of at least 25 ce or any other 
equally accurate method, making the test at 15.5°C, water 
being unity at 15.5°C. . 

(d) Actip NuMBER.—Weigh from 5 to 10 g of the oil. Transfer. 
to a 350 cc Erlenmeyer flask. Add 50 cc of neutral 95 per cent 
ethyl alcohol. Put a condenser loop inside the neck of the flask. 
Heat on a steam bath for 30 minutes. Cool and add phenol- 
phthalein indicator. Titrate to a faint permanent pink color 
with the standard sodium hydroxide solution. Calculate the 
acid number (milligrams KOH per gram of oil). 

(e) SAPONIFICATION NUMBER.—Weigh about 2 g of the oil in 
a 350 cc Erlenmeyer flask. Add 25 cc alcoholic sodium hydroxide 
solution. Put a condenser loop inside the neck of the flask and 
heat on the steam bath for one hour. Cool, add phenolphthalein 
as indicator, and titrate with half normal sulphuric acid. Run 
two blanks with the alcoholic sodium hydroxide solution. (See 
4(h).) ‘These should check within 0.1 cc N/2 H,5O,. From the 
difference between the number of cubic centimeters of N/2 H,50, 
required for the blank and for the determination, calculate the 
saponification number (milligrams KOH required for 1 g of oil). 

({) UNSAPONIFIABLE MaTreR.—Weigh 8 to 1o g of the oil. 
Transfer to a 250 cc, long-neck flask. Add 5 cc of strong solu- 
tion of sodium hydroxide (equal weights of NaOH and H,0), 
and 50 ce 95 per cent ethyl alcohol. Put a condenser loop inside 
the neck of the flask and boil for two hours. Occasionally agitate 
the flask to break up the liquid but do not project the liquid 
onto the sides of the flask. At the end of two hours remove the 
condenser and allow the liquid to boil down to about 25 ce. 

Transfer to a 500 cc glass-stoppered separatory funnel, rinsing 
with water. Dilute with water to 250 cc, add 100 ce redistilled 
ether. Stopper and shake for one minute. Let stand until the 
two layers separate sharp and clear. Draw all but one or two 
drops of the aqueous layer into a second 500 ce separatory funnel 
and repeat the process using 60 cc of ether. After thorough 
separation draw off the aqueous solution into a 400 cc beaker, 
then the ether solution into the first separatory funnel, rinsing 
down with a little water. Return the aqueous solution to the 
second separatory funnel and shake out again with 60 cc of ether 
in a similar manner, finally drawing the aqueous solution into the 
beaker and rinsing the ether into the first separatory funnel. 


6 Circular of the Bureau of Standards 


Shake the combined ether solution with the accumulated water 
rinsings and let the layers separate sharp and clear. Draw off 
the water and add it to the main aqueous solution. Shake the 
ether solution with two portions of water (about 25 ce each). 
Add these to the main water solution. | 


Swirl the separatory funnel so as to bring the last drops of 


water down to the stopcock, and draw off until the ether solution 
just fills the bore of the stopcock. Wipe out the stem of the 
separatory funnel with a bit of cotton on a wire. Draw the 
ether solution (portionwise if necessary) into a 250 ce flask and 
distill off. While still hot, drain the flask into a small weighed 
beaker, rinsing with a little ether. Evaporate this ether, cool 
and weigh. (The unsaponifiable oil from adulterated drying oils 
as volatile and will evaporate on long heating. Therefore heat the 
beaker on a warm plate, occasionally blowing out with a current of 


dry air. Discontinue heating as soon as the odor of ethers gone.) 


(g) loping NumBER.—Place a small quantity of the sample in a 


small weighing burette or beaker. Weigh accurately. ‘Transfer 


by dropping about 0.15 g (0.10 to 0.20 g) to a 500 ee bottle having 
a well-ground glass stopper, or an Erlenmeyer flask having a 
specially flanged neck for the iodine test. Reweigh the burette 
or beaker and determine the amount of sample used. Add 10 
ce of chloroform. Whirl the bottle to dissolve the sample. Add 
10 cc of chloroform to two empty bottles like that used for the 
sample. Add to each bottle 25 ce of the Hanus solution (see 
4 (g)) and let stand with occasional shaking for one-half hour. 
Add 10 ce of the 15 per cent potassium iodide solution and 100 
ce of water, and titrate with standard sodium thiosulphate using 
starch as indicator. ‘The titrations on the two blank tests should 
agree within 0.1 cc. From the difference between the average 
of the blank titration and the titration on the samples and the 
iodine value of the thiosulphate solution, calculate the iodine 
number of the samples tested. (Iodine number is centigrams of 
iodine to 1 g of sample.) pa } 

(h) Asu.—Tare a porcelain crucible or dish. Add 10 to 2 5 ce 
of oil, carefully weighing the amount added. Place on a stone 
slab on the floor of a hood. Ignite by playing the flame of a 
burner on the surface of the oil and allow to burn quietly until 
most of the oil is burned off; then transfer to a muffle or over a 
flame and-continue heating at a very low temperature (not over 
a dull red) until all carbonaceous matter is consumed. Cool. 


oe at al 


Linseed Oil | 


weigh, and calculate the percentage of.ash. Moisten the ash with 
a few drops of water and test with litmus paper. Record whether 
neutral or alkaline. Wash any ash adhering to the test paper 
back into the crucible. Dissolve the ash in dilute nitric acid to 
which a little hydrogen peroxide has been added. After solution 
is complete make up the volume to about 50 ce with nitric acid 
and water so that the final volume will contain about 1 volume of 
concentrated nitric acid and 3 volumes of water. Boil to remove 
excess of hydrogen peroxide. Determine manganese by the bis- 
muthate method as described in Treadwell-Hall, Analytical 
Chemistry, third edition, volume 2, page 617. 

Ash another portion of the oil and dissolve the ash as above 
in nitric acid and hydrogen peroxide. Transfer to a 250 cc beaker _ 
and dilute to about 200 cc. This volume of solution should con- 
tain 15 to 20 cc of concentrated nitric acid. LElectrolyze this 
solution using platinum electrodes (the anode being previously 
weighed) with a current densjty of about 0.5 ampere and 2 to 
2.5 volts. It is best to pass the current overnight (about 15 
hours). On removing the anode, it is carefully washed in clear 
water, dried in a steam oven, transferred to an oven where it is _ 
heated to 180° C, cooled and weighed. ‘The increase in weight 
of the anode multiplied by 0.86 gives the weight of lead in the 
sample. Calculate to percentage. If desired, the lead may be 
determined by the sulphate or any other accurate method in 
place of the electrolytic method given above. 

(1) Time or Dryinc on GLass.—Flow the oil over a perfectly 
clean, glass plate and allow to drain in a vertical position in a 
well-ventilated room at a temperature between 15 and 39° C.. 
After about 2 hours the film is tested at intervals with the finger 
at points not less than 214 cm from the edges. The film will be 
considered dry when it adheres no longer to the finger and does 
not rub up appreciably when the finger is rubbed lightly across 
‘the surface. With boiled linseed oil this usually occurs in from 
5 to 18 hours. 

(7) Color.—Prepare a fresh solution of pure potassium bichro- 
mate in pure strong (1.84 specific gravity) colorless sulphuric 
acid. For raw oil, this solution should be in the proportion of 
1.0 g potassium bichromate to 100 cc (184.0 g) sulphuric acid. 
For refined oil, the solution should be in the proportion of 0.1 g 
potassium bichromate to 100 ce sulphuric acid. Place the oil 
and colored solution in separate thin-walled, clear glass tubes of 


8 Circular of the Bureau of Standards 


the same diameter (1 to 2 cm) to a depth of not less than 2.5 cm 
and compare the depths of color by looking transversely pate 
the columns of liquid by transmitted light. 


4. REAGENTS FOR TESTING 


The following reagents will be required: 

(a) ACETONE that will pass the specification of the United 
States Pharmacopoeia. 

(b) Actp CaLcIuM CHLORIDE SOLUTION.—Saturate with calcium 
chloride a mixture of 90 parts water and ro parts concentrated 
hydrochloric acid (specific gravity 1.2). 

(c) SraNDARD SopruM THIOSULPHATE SOLUTION.—Dissolye pure 
sodium thiosulphate in distilled water that has been well boiled 
to free it from carbon dioxide in the proportion so that 24.83 g 
crystallized sodium thiosulphate will be present in 1000 ce of the 
solution. It is best to let this solution stand for about two 
weeks before standardizing. Stardardize with pure resublimed 
iodine. (See Analytical Chemistry, Treadwell-Hall, Vol. II, 3d 
ed., p. 646.) This solution will be approximately decinormal, 
and it is best to leave it as it is after determining its exact iodine 
value, rather than to attempt to adjust it to exactly decinormal 
strength. Preserve in a stock bottle provided with a guard tube 
filled with soda lime. 

(d) StarcH SoLUTION.—Stir up 2 to 3 g of potato starch or 
5 g soluble starch with 100 cc of 1 per cent salicylic acid solution, 
add 300 to 400 cc boiling water, and boil the mixture until the 
starch is practically dissolved. Dilute to x liter. 

(ec) STANDARD IODINE SOLUTION.—Dissolve 13 g of resublimed 
iodine and 18 g of pure potassium iodide (free from iodates) in 
50 cc of distilled water, and dilute to 1000 cc. Determine its 
exact value by titrating with the standard sodium thiosulphate 
solution. 

(7) Porasstum IopipE SOLUTION.—Dissolve 150 g of potassium 
iodide free from iodate in distilled water and dilute to 1000 cc. 

(g) Hanus So_ution.—Dissolve 13.2 g of iodine in 1000 ce of 
glacial acetic acid (99.5 per cent) that will not reduce chromic 
acid. Add enough bromine to double the halogen content, de- 
termined by titration (3 cc of bromine is about the proper amount). 
The iodine may be dissolved by the aid of heat, but the solution 
should be cold when the bromine is added. 


Linseed Oul. 9 


(h) STANDARD SODIUM HypDROXIDE SOLUTION.—Prepare a stock 
concentrated solution of sodium hydroxide by dissolving sodium 
hydroxide in water in the proportion of 200 g NaOH to 200 cc 
water. Allow this solution to cool and settle in a stoppered 
bottle for several days. Decant the clear liquid from the precipi- 
tate of sodium carbonate into another clean bottle. Add clear 
barium hydroxide solution until no further precipitate forms. 
Again allow to settle until clear. Draw off about 175 cc and 
dilute to 10 liters with freshly boiled distilled water. Preserve 
in a stock bottle provided with a large guard tube filled with 
soda lime. Determine the exact strength by titrating against 
pure benzoic acid (C,H,COOH) using phenolphthalein as indi- 
cator. (See Bureau of Standards Scientific Paper 183.) This 
solution will be approximately one-fourth normal, but do not 
attempt to adjust it to any exact value. Determine its exact 
strength and make proper corrections in using it. 

(i) ALconoLic Soprum HypRoxIDE SoLUTION.—Dissolve pure 
sodium hydroxide in 95 per cent ethyl alcohol in the proportion 
of about 22 g per 1000 cc. Let stand in a stoppered bottle. 
Decant the clear liquid into another bottle, and keep well stop- 
pered. This solution should be colorless or only slightly yellow 
when used; it will keep colorless longer if the alcohol is previously 
treated with NaOH (about 80 g to 1000 cc), kept at about SODAS 
for 15 days, and then distilled. : 

(j) Hay Normal SULPHURIC ACID SoLuTIon.—Add about 15 
ec sulphuric acid (1.84 specific gravity) to distilled water, cool 
and dilute to 1000 ce. Determine the exact strength by titrating 
against freshly standardized sodium hydroxide or by any other 
accurate method. Either adjust to exactly half normal strength 
or leave as originally made, applying appropriate correction. 


5. BASIS OF PURCHASE 


Material is to be purchased by weight or volume as specified in 
the contract. When purchased by weight, the price shall be 
quoted per pound or per hundred pounds. When purchased by 
volume, a gallon of oil shall mean 231 cubic inches, at 15.5° C. 


ADDITIONAL COPIES 
OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 
AT 
5 CENTS PER COPY 


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DEPARTMENT OF COMMERCE. 
BUREAU OF STANDARDS. 


S. W. STRATTON, Director. 


CIRCULAR OF THE BUREAU OF STANDARDS. 


No. 84. 


[2d edition. Issued July 3, 1922.] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
BASIC CARBONATE WHITE LEAD, DRY AND PASTE, 


FEDERAL SPE@JFICATIONS BOARD. 
STANDARD SPECIFICATION NO. 5. 


This Specification was officially adopted by the Federal Specifications Board on 
February 3, 1922, for the use of the Departments and Independent Establish- 


ments of the Government in the purchase of materials covered by it. 


CONTENTS. 
Page 
Teel IE MS, ei Be LY 2 ep I 
en, eee ee ee ee, 2 
3. Laboratory examination of dry pigment.........................-.-... 2. 3 
4. Laboratory examination of paste...........:...... Bis OS Rae dds TREE 4 
eS Oa re es a OG an Rae a Ok 7 


1. GENERAL. 


Basic carbonate white lead may be ordered in the form of dry 
pigment or paste ground in linseed oil. Material shall be pur- 
chased by net weight. 

(2) Dry PicmMeNnt.—The pigment shall be the product made 
from metallic lead and shall have a composition corresponding 
approximately to the formula 2PbCO,.Pb(OH),. It shall be 
thoroughly washed after corroding, shall be free from impurities 
and adulterants, and shall meet the following requirements: 

106568 °—24 


2 Circular of the Bureau of Standards 


Color—Color strength.—When specified, shall be equal to that 
of a sample mutually agreed upon by buyer and seller. 


I pa sn omer 
Minimum, | Maximum. 


a 


Per cent. | Per cent. 


Coarse particles retained on Standard No. 325 SCFeeN............ 2 cee ndt een eee efasar ere canes 1.0 
Fead carbomate,.. cc. veg. occs cyece epee ls home esinee nine shove’ al 1008s s Gees 65. 0 75.0 
Total impurities, including moisture..........-..+++++rerreeesstrrertseetetetetstestsssses ees 2.0 


(b) Paste.—The paste shall be made by thoroughly grinding 
the above-described pigment with pure raw or refined linseed oil. 
The paste as received shall not be caked in the container and 


shall break up readily in oil to form a smooth paint of brushing 


consistency. ‘The paste shall consist of: 


ee 
Minimum. | Maximum. 


a 


Pigment) 2002 dic tels ones coco tensed seus tenann na ea» Vester a ata hi 
Linseed Of)... oc ss cede ecu se cacweessae ema aes Ap at ho «bin sivs sy fee rs 8 10 
Moisture and other volatile matter............. 0.0. .e ee ece terete ete nee eee elec eee ee eeees 0.7 
Coarse particles and ‘‘skins’’ (total residue retained on No. 325 screen based on 

pigment)... ...ce.ciseeceenecenseecuneeeaueee cee snl ens tanianhi)s at AN ois se 1.5 


a 


Nore.—Deliveries will, in general, be sampled and tested by the following methods, but the purchaser 
reserves the right to use any additional available information to ascertain whether the material meets the 


specification. 
2. SAMPLING. 


It is mutually agreed by buyer and seller that a single package 
out of each lot of not more than 1,000 packages shall be taken as 
representative of the whole. 

With the dry pigment, this package shall be opened by the 
inspector and a sample of not less than 5 pounds taken at random 
from the contents and sent to the laboratory for test. When 
requested, a duplicate sample may be taken from the same pack- 
age and delivered to the seller, and the inspector may take a 
third sample to hold for test in case of dispute. 

Whenever possible, an original unopened container shall be 
sent to the laboratory with the paste; and when this is for any 
reason not done, the inspector shall determine by testing thor- 
oughly with a paddle or spatula whether the material meets the 
requirement regarding not caking in the container. (See 4 (a).) 
After assuring himself that the paste is not caked, the inspector 
shall draw a sample of not less than 5 pounds of the thoroughly 
mixed paste, place it in a clean dry metal or glass container, 
which must be filled with the sample, closed with a tight cover, 
sealed, marked, and sent to the laboratory for test with the 
inspector’s report on caking in container. . 


Specification jor Basic Carbonate White Lead, Dry and Paste 3 
3. LABORATORY EXAMINATION OF DRY PIGMENT. 


(a) CoLlor.—Take 1 g of the sample, add 10 to 12 drops linseed 
oil, rub up on a stone slab or glass plate with a flat-bottomed 
glass or stone pestle or muller to a uniform smooth paste. Treat 
in a similar manner 1 g of the standard basic carbonate white 
lead. Spread the two pastes side by side on a glass microscope ) 
slide and compare the colors. If the sample is as white or whiter 
than the ‘‘standard,”’ it passes this test. If the standard is whiter 
than the sample, the material does not meet the specification. 

(b) CoLoR STRENGTH.—Weigh accurately 0.01 g of lampblack, 
place on a large glass plate or stone slab, add 5 drops of linseed 
oil, and rub up with a flat-bottomed glass pestle, or muller, then 
add exactly 10 g of the sample and 45 drops of linseed oil, and 
grind with a circular motion of the muller 50 times; gather up 
with a sharp-edge spatula and grind out two more times in a 
like manner, giving the pestle a uniform pressure. Treat another 
0.01 g of the same lampblack in the same manner, except that 1o 
g of standard basic carbonate white lead is used instead of the 10 
g of the sample. Spread the two pastes side by side on a glass 
microscope slide and compare the colors. If the sample is as 
light or lighter in color than the standard, it passes this test. If 
the standard is lighter in color than the sample, the material does 
not meet the specification. 

(c) Coarse ParTICLES.'—Dry in an oven at 105° to 110° C. a 
No. 325 screen, cool and weigh accurately. Weight 25 g of the 
sample; dry at 100° C.; transfer to a mortar, add 100 cc kero- 
sene, thoroughly mix by gentle pressure with a pestle to break 
up all lumps, wash with kerosene through the screen, breaking 
up all lumps, but not grinding. After washing with kerosene 
until all but the particles which are too coarse to pass the screen 
have been washed through, wash all kerosene from the screen with 
ether or petroleum ether, heat the screen for one hour at 105 to 
110° C., cool and weigh. 

(d) QUALITATIVE ANALYSIS.—Test for matter insoluble in acetic 
acid, zinc, calcium, etc., by the regular methods of qualitative 
analysis. 

(ec) MorsruRE.—Place 1 g of the sample in a tared wide-mouth 
short weighing tube provided with a glass stopper. Heat with 


tie fey en 

1 For a general discussion of screen tests of pigments and data regarding many pigments on the market, 
see Circular No. 148 of the Educational Bureau, Scientific Section, Paint Manufacturers’ Association of 
the United States. 


4 Circular of the Bureau of Standards 


stopper removed for two hours at a temperature between 105 and 
110°C. Insert stopper, cool and weigh. Calculate loss in weight 
as moisture. 

(f) Tota, LEAD AND INSOLUBLE ImpuRITY.—Weigh 1 g of the 
sample, moisten with water, dissolve in acetic acid. If any insol- 
uble residue remains, filter, dry at 105 to 110° C. and weigh as 
insoluble impurity. Dilute the solution to about 200 ec, make 
alkaline with NH,OH, then acid with acetic acid, heat to boiling 
and add ro to 15 cc of a 10 per cent solution of sodium bichromate 


or potassium bichromate, and heat until the yellow precipitate 


assumes an orange color. Let it settle and filter on a Gooch 
crucible, washing by decantation with hot water until the wash- 
ings are colorless, and finally transferring all the precipitate. 
Then wash with 95 per cent ethyl alcohol and then with ethyl 
ether; dry at 100° C. and weigh PbCrO,. Calculate to lead oxide 


(PbCrO, x0.69=PbO). Total lead may be determined by the 


sulphate method if preferred. 

(g) CARBON Diox1DE.—Determine by evolution with dilute acid 
and absorption in soda-lime or KOH solution, calculate CO, to 
PbCO,, subtract PbO equivalent from total PbO and calculate 
residual PbO to Pb(OH),. 

CO; x6.072 = PbCO, 

CO, X 5.072 =Fpw 
PbO X 1.197 = PbCOz 
PbO X 1.08 =Pb(OH), 


4. LABORATORY EXAMINATION OF PASTE. 


(a2) CAKING IN CONTAINER.—When an original package is 
received in the laboratory, it shall be weighed, opened, and 
stirred with a stiff spatula or paddle. The paste must be no 
more difficult to break up and show no more caking than a normal 
good grade of white-lead paste. The paste shall finally be thor- 
oughly mixed, removed from the container, and the container 
wiped clean and weighed. This weight subtracted from the 
weight of the original package gives the net weight of the contents. 
A portion of thoroughly mixed paste shall be placed in a clean 
container and the portions for the remaining tests promptly 
weighed out. 

(6) MixiInc witH LINSEED O1,.—One hundred grams of the 
paste shall be placed in a cup, 30 cc linseed oil added slowly with 


a 


Specification for Basic Carbonate White Lead, Dry and Paste 5 


careful stirring and mixing with a spatula or paddle. ‘The result- 
ing mixture must be smooth and of good brushing consistency. 

(c) MOISTURE AND OTHER VOLATILE MATTER.—Weigh accu- 
rately from 3 to 5 g of the paste into a tared flat-bottomed dish, 
about 5 cm in diameter, spreading the paste over the bottom. 
Heat at 105 to 110° C. for one hour, cool and weigh. Calculate 

loss in weight as percentage of moisture and other volatile matter. 
_ (d) PERCENTAGE oF PIGMENT.—Weigh accurately about 15 g 
of the paste into a weighed centrifuge tube. Add 20 to 30 cc 
“extraction mixture”’ (see Reagents), mix thoroughly with a glass 
rod, wash the rod with more of the extraction mixture, add 
enough of the reagent to make a total of 60 cc in the tube. Place 
the tube in the, container of a centrifuge, surround with water 
and counterbalance the container of the opposite arm with a 
similar tube or a tube with water. Whirl at a moderate speed 
until well settled. Decant the clear supernatant liquid. Repeat 
the extraction twice with 4o cc of the extraction mixture, and 
once with 40 cc of ether. After drawing off the ether, set the 
tube in a beaker of water at about 80° C., or on top of a warm 
oven for 10 minutes, then in an oven at 110 to 11 5° C. for two 
hours. Cool, weigh, and calculate the percentage of pigment. 

(e) EXAMINATION OF PIGMENT.—Grind the pigment from (d) 
to a fine powder, pass through a No. 80 screen to remove any 
“skins,” preserve in a stoppered tube and apply tests 3(a), 3(b), 
3(d), 3(7), and 3(g). 

(7) PREPARATION oF Fatty Actps.—To about 25 g of the paste 
in a porcelain casserole add 15 cc of aqueous sodium hydroxide 
(see reagents) and 75 cc of ethyl alcohol, mix and heat uncovered 
on a steam bath until saponification is complete (about one hour). 
Add 100 cc of water, boil, add sulphuric acid of specific gravity 
1.2 (8 to 10 cc in excess), boil, stir, and transfer to a separatory 
funnel to which some water has been previously added. Draw 
off as much as possible of the acid aqueous layer and lead 
sulphate precipitate, wash once with water: then add 50 cc 
of water and 50 cc of ether. Shake very gently with a whirl- 
ing motion to dissolve the fatty acids in the ether, but not so 
violently as to form an emulsion. Draw off the aqueous layer 
and wash the ether layer with one 15 cc portion of water and then 
with 5 cc portions of water until free from sulphuric acid. Then 
draw off the water layer completely. Transfer the ether solution 
to a dry flask, add 25 to 50 g of anhydrous sodium sulphate. 


6 Circular of the Bureau of Standards 


Stopper the flask and let stand with occasional shaking at a tem- 
perature below 25° C. until the water is completely removed from 
the ether solution, which will be shown by the solution becoming 
perfectly clear above the solid sodium sulphate. Decant this clear 
solution (if necessary through a dry filter paper) into a dry 100 cc 
Erlenmeyer flask. Pass a rapid current of dry air (pass through a 
CaCl, tower) into the mouth of the Erlenmeyer flask and heat ata 
temperature below 75° C. on a dry hot plate until the ether is 
entirely driven off. . 

Norx.—It is important to follow all of the details, since ether generally contains 
alcohol and after washing with water always contains water. It is very difficult 
to remove water and alcohol by evaporation from fatty acids, but the washing of the 
ether solution and subsequent drying with anhydrous sodium sulphate removes both 


water and alcohol. Ether, in the absence of water and alcoliol, is easily removed 
from fatty acids by gentle heat. 


The fatty acids prepared as above should be kept in a stoppered © 


flask and examined at once. 
(g) TEST FOR MINERAL O1.—Place 10 drops of the fatty acid 


(f) in a 50 cc test tube, add 5 cc of alcoholic soda (see reagents), 


boil vigorously for five minutes, add 40 cc of water and mix. 
A clear solution indicates absence of more than a trace of unsaponi- 
fiable matter. If the solution is not clear, the oil is not pure 
linseed oil. 

(hk) lopINE NUMBER OF Farry Acips.—Place a small quantity 
of the fatty acids (f) in a small weighing burette or beaker. Weigh 
accurately. Transfer by dropping about 0.15 g (0.10 to 0.20 g) 
to a 500 cc bottle having a well-ground glass stopper, or an 
Erlenmeyer flask having a specially flanged neck for the iodine 
test. Reweigh the burette or beaker and determine the amount 
of sample used. Add ro cc of chloroform. Whirl the bottle 
to dissolve the sample. Add 10 cc of chloroform to two empty 
bottles like that used for the sample. Add to each bottle 25 cc 
of the Hanus solution (see reagents) and let it stand with occa- 
sional shakings for one-half hour. Add 10 ce of the 15 per cent 
potassium-iodide solution and 100 cc of water, and titrate with 
standard sodium thiosulphate, using starch as indicator. The ti- 
tration on the two blank tests should agree within 0.1 cc, From 
the difference between the average of the blank titrations and 
the titration on the sample, and the iodine value of the thiosul- 
phate solution, calculate the iodine number of the sample tested. 
(Iodine number is centigrams of iodine to 1 g of sample.) If 


ee ee ae ee Se 


Specification for Basic Carbonate White Lead, Dry and Paste 7 


the iodine number is less than 170, the oil does not meet the 
specification. 

(i) COARSE PARTICLES AND ‘“‘SKINS.”—Weigh an amount of 
paste containing 25 g of pigment (see 4 (d)), add roo cc kero- 
sene, wash through a No. 325 screen and weigh the residue as in 
arte): 

5. REAGENTS. 


(a) ExTRACTION MIxTURE— 
10 volumes ether (ethyl ether). 
6 volumes benzol. 
4 volumes methyl alcohol. 
1 volume acetone. 


(6) AQguEOuS Soprum HyproxIpE.—Dissolve 100 g sodium 
hydroxide in distilled water and dilute to 300 cc. 

(c) STANDARD SODIUM ‘THIOSULPHATE SOLUTION.—Dissolve 
pure sodium thiosulphate in distilled water that has been well 
boiled to free it from carbon dioxide, in the proportion of 24.83 g 
crystallized sodium thiosulphate to 1,000 cc of the solution. 
It is best to let this solution stand for about two weeks before 
standardizing. Standardize with pure resublimed iodine.” This 
solution will be approximately decinormal, and it is best to leave 
it as it is after determining its exact iodine value, rather than to 
attempt to adjust it to exactly decinormal. Preserve in a stock 
bottle provided with a guard tube filled with soda lime. 

(d) STARCH SOLUTION.—Stir up 2 to 3 g of potato starch or 
5 g of soluble starch with too ce of 1 per cent salicylic acid 
solution, add 300 to aoo cc of boiling water, boil the mixture 
until the starch is practically dissolved, and then dilute to one 
liter. 

(e) Porasstum IopIDE SOLUTION. —Dissolve 150 g potassium 
iodide free from iodate in distilled water and dilute to 1,000 cc. 

(7) Hanus So_utron.—Dissolve 13.2 g iodine in 1,000 cc of 
glacial acetic acid, 99.5 per cent, which will not reduce chromic 
acid. Add enough bromine, about 3 cc to double the halogen 
content, which is determined by titration. The iodine may be 
dissolved by applying heat, but the solution should be cold when 
the bromine is added. | . 

(g) ALCOHOLIC SopIUM-HYDROXIDE SOLUTION.—Dissolve pure 
sodium hydroxide in 95 per cent ethyl alcohol in the proportion of 


2 See Treadwell-Hall Analytical Chemistry, I], 3d ed., p. 646. 


8 Circular of the Bureau of Standards 


about 22 g per 1,000 cc. Let the solution stand in a stoppered 
bottle. Decant the clear liquid into another bottle, and keep well 
stoppered. This solution should be colorless or only slightly 
yellow when used, and it will keep colorless longer if the alcohol is 
previously treated with NaOH (about 80 g to 1,000 cc), kept at 
about 50° C. for 15 days, and then distilled. 


ADDITIONAL COPIES 
OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 
AT 


5 CENTS PER COPY 
V 


WASHINGTON : GOVERNMENT PRINTING OFFICE : 1924 


DEPARTMENT OF COMMERCE. 
BUREAU OF STANDARDS. 


S. W. STRATTON, Director. 


CIRCULAR OF THE BUREAU OF STANDARDS. 
No. 85. 


[2d edition. Issued July 3, 1922.] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
BASIC SULPHATE WHITE LEAD, DRY AND PASTE. 


es 


FEDERAL SPECIFICATIONS BOARD. 
STANDARD SPECIFICATION NO. 6. 


This Specification was officially adopted by the Federal Specifications Board on 
February 3, 1922, for the use of the Departments and Independent Estab- 
lishments of the Government in the purchase of materials covered by it. 


CONTENTS. 
Page 
AT RM Tos. PRS oon eke St EP Eee bis fe Phare ee I 
Merete me renee CPOE Ge BE, tteis al a he ae oF Sd Be 2 
S.:Laborsary examination of dry pigment): !) i). ui du. biiee an A 2 
eet el Oe TIENT OL DASte Fs. ow sce sien, posh mlenyn'e anita w Aa seb vok ‘ 
SnaNMNE Teme re sesh, Sh Pa at OEE RA OE ARE, | ee Res 7 


1. GENERAL. 


Basic sulphate white lead may be ordered in the form of dry 
pigment or paste ground in linseed oil. Material shall be pur- 
chased by net weight. 

(2) Dry Picment.—The pigment shall be the sublimed product 
prepared from lead sulphide ores, free from impurities and adul- 
terants, and shall meet the following requirements: 

Color—Color Strength.—When specified shall be equal to that of 
a sample mutually agreed upon by buyer and seller. 


Minimum. | Maximum. 


Coarse particles: ~ Per cent. | Per cent. 
etabied. on Mandard Nov425.acreen=: . sor vty oo. 4. 08.8 BSD ee ek ewe 1.0 
Composition: 
RC ERE rece te ty eae hag eee ine ce chase Cost ae ieee 11.0 18.0 
CAT GEO C ihe aole cts oy 6 te Eg Te Oe eA Pi ee TIS AO RBG a oR 9.0 
20al impudties, including moisture ooo es us Has sob en ddd wes wivewsetuasacdpeuwOsaiaves 1.0 


The remainder shall be lead sulphate. 


a 


104952°—24——-1 


2 Circular of the Bureau of Standards 


(b) PasteEs.—The paste shall be made by thoroughly grinding 
the dry pigment with pure raw or refined linseed oil. 

The paste as received shall not be caked in the container and 
shall break up readily in oil to form a smooth paint of brushing 
consistency. It shall mix readily in all proportions without 
curdling with linseed oil, turpentine, or volatile mineral ie 
or any combination of these substances. 

The paste shall consist of: 


ees 
Per Sori 
[ko (991) 1) eg erry aed CON EDR EO LRM MGR OMANI EM am 1.0 
Pinseed Oil... Bak sh ioe oe a ks Me a BOY ee eee rN 0 
Moisture and other volatile: matter...) occ. css cies wse.pesiecls selssens « ve ee ee 0.7 
Coarse particles and ‘‘skins”’ ( totai residue retained on No. 325 screen, based on 
PUTMNCTL) ee eed aa ce ba banaue baccevs sce un/be wb oals meu o/h-cln a alkene an 1.5 


Note.—Deliveries will, in general, be sampled and tested by the following methods, but the purchaser 
reserves the right to use any additional available information to ascertain whether the © matety meets 


the specification. 
2. SAMPLING. 


It is mutually agreed by buyer and seller that a single package 
out of each lot of not more than 1,000 packages shall be taken as 
representative of the whole. 

With the dry pigment, this package shall be opened by the 
inspector and a sample of not less than 5 pounds taken at random 
from the contents and sent to the laboratory for test. 

With the paste, whenever possible, an original unopened con- 
tainer shall be sent to the laboratory; and when this is for any 
reason not done, the inspector shall determine, by thorough test- 
ing with a paddle or spatula, whether the material meets the 
requirement regarding not caking in the container. (See 4a.) 
After assuring himself that the paste is not caked in the container 
the inspector shall draw a sample of not less than 5 pounds of the 
thoroughly mixed paste, place it in a clean dry metal or glass con- 
tainer, which must be filled with the sample, closed with a tight 
cover, sealed, marked, and sent to the laboratory for test with the 
inspector’s report on caking in container. 

When requested, a duplicate sample may be taken from the 
same package and delivered to the seller, and the inspector may 
take a third sample to hold for test in case of dispute. 


3. LABORATORY EXAMINATION OF DRY PIGMENT. 


(a) CoLor.—Take 1 g of the sample, add ro to 12 drops linseed 
oil, rub up on a stone slab or glass plate with a flat-bottomed glass 
or stone pestle or muller to a uniform smooth paste. Treat in 


Specification for Basic Sulphate White Lead, Dry and Paste 3 


a similar manner, 1 g of the standard basic sulphate white lead. 
Spread the two pastes side by side on a glass microscope slide and 
compare the colors. If the sample is as white as or whiter than the 
“standard,” it passes this test. If the ‘‘standard’’ is whiter than 
the sample, the material does not meet the specification. 

(6) CoLor StRENGTH.— Weigh accurately o.o1 g of lampblack, 
place on a large glass plate or stone slab, add 5 drops of linseed oil 
and rub up with a flat-bottomed glass pestle or muller, then add 
exactly 10 g of the sample and 45 drops of linseed oil and grind 
with a circular motion of the muller 50 times; gather up with 
a sharp-edge spatula and grind out twice more in a like manner, 
giving the pestle a uniform pressure. ‘Treat another 0.01 g of the 
satne lampblack in the same manner except that 10 g of standard 
basic sulphate white lead is used instead of the 10 g of the sample. 
Spread the two pastes side by side on a glass microscope slide and 
compare the colors. If the sample is as light as or lighter in color 
than the ‘‘standard,”’ it passes this test. If the ‘‘standard’’ is 
lighter in color than the sample, the material does not meet the 
specification. 

(c) COARSE PaRTICLES.'—Dry in an oven at 105 to 110° C. a 
No. 325 screen, cool, and weigh accurately. Weigh 25 g of the 


~ sample, dry at 10o0°C.; transfer to a mortar, add 100 cc kerosene, 


thoroughly mix by gentle pressure with a pestle to break up all 
Jumps, wash with kerosene through the screen, breaking up all 
lumps but not grinding. After washing with kerosene until all 
but the particles too coarse to pass the screen have been washed 
through, wash all kerosene from the screen with ether or petroleum 
ether, heat the screen for one hour at 105 to 110° C., cool, and 
weigh. 

(d) QUALITATIVE ANALYSIS. —Test for matter insoluble in 
acid ammonium acetate solution, for calcium, for carbonates, 
and for any other impurities suspected by the regular methods of 
qualitative analysis. 

(e) MorsturE.—Place 1 g of the sample in a tared, wide mouth, 
short weighing tube provided with a glass stopper. Heat with 
Aig removed for two hours'at a temperature between 105 and 
110°C. Insert stopper, cool, and weigh. Calculate loss in weight 
as moisture. 


1 For a general discussion of screen tests of pigments and data regarding many pigments on the market, 
see Circular No. 148 of the educational bureau, scientific section, Paint Manufacturers’ Association of the 
United States. 


4 Circular of the Bureau of Standards 


(f) INSOLUBLE ImpuRITY AND ToTaL LeEapD.—In a 250 cc 
beaker, moisten 1 g of the pigment with a few drops of alcohol; 
add 50 cc of acid ammonium acetate solution. (See Reagents 
5a.) Heat to boiling and boil for 2 minutes. Decant through a 
filter paper, leaving any undecomposed matter in the beaker. To 
the residue in the beaker, add 50 ce of the acid ammonium acetate 
solution, heat to boiling, and boil for 2 minutes. Filter through - 
the same paper and wash with hot water. If an appreciable 
residue remains, ignite and weigh as insoluble impurity. Unite 
the acid ammonium acetate solutions, heat to boiling, and add 
dropwise, with stirring, a slight excess (in total about 10 to 15 cc) 
of dichromate solution. (See Reagents 55.) Heat until the 
precipitate assumes an orange color, let settle, filter on a weighed 
Gooch crucible, wash by decantation with hot water until the 
washings are colorless, and finally transfer all of the precipitate 
to the crucible. Then wash with 10 cc of 95 per cent ethyl 
alcohol and finally with rocc of ethyl ether. Dry at 110 to 120° 
C., cool, and weigh PbCrO,. Calculate to PbO by multiplying 
by the factor 0.69. 

(g) Zinc Ox1DE.—Weigh accurately about 1 g of the pigment, 
transfer to a 400 cc beaker, add 30 ce of HCl (1:2), boil for 2 or 
3 minutes, add 200 cc of water and a small piece of litmus paper, 
add NH,OH until slightly alkaline, render just acid with HCl, 
then add 3 cc of concentrated HCl, heat nearly to boiling, and 
titrate with standard potassium ferrocyanide as in standardizing 
that solution. (See Reagents 5d.) Calculate total zinc as ZnO. 

(h) LEAD SULPHATE.—Treat 0.5 g of the pigment in a 400 cc 
beaker with a few drops of alcohol, add 10 ce of bromine water, 
toccof HCl (1:1), and 3 g of NH,Cl. Cover with a watch glass 
and heat on a steam bath for 5 minutes, add hot water to give a 
total volume of about 200 ce, boil for 5 minutes, filter to separate 
any insoluble matter (a pure pigment should be completely dis- 
solved), and wash thoroughly with hot water. (The insoluble 
matter may be ignited, weighed, and examined qualitatively.) 
Neutralize the clear solution (original solution or filtrate from 
insoluble matter) in a covered beaker with dry Na,CO,, add 1 g 
more of dry Na,CO,, and boil 10 to 15 minutes. Wash off cover, 
let settle, filter, and wash with hot water. Redissolve the precipi- 
tate in HCl (1:1), reprecipitate with Na,CO, as above, filter, and 
wash thoroughly with hot water. Acidify the united filtrates 
with HCl, adding about 1 cc in excess. Boil to expel bromine, 


Specification for Basic Sulphate White Lead, Dry and Paste 5 


and to the clear boiling solution add slowly with stirring 15 cc of 
barium chloride solution. (See Reagents 5¢.) Let stand on 
steam bath for about one hour, filter on a weighed Gooch crucible, 
wash thoroughly with boiling water, dry, ignite, cool, and weigh 
as BaSO,. Calculate to PbSO,, using the factor 1. Co : 

(4) CaLCULATIONS.—Calculate the percentage of PbSO, to PbO 
by multiplying by the factor 0.736 and subtract the result from 
the percentage of PbO found under (f); report the difference as 
PbO. Report ZnO found under (g) as percentage of ZnO. Mois- 
ture and insoluble matter are reported as such.’ 


4, LABORATORY EXAMINATION OF PASTE. 


(aq) CAKING IN CONTAINER.—When an original package is 
received in the laboratory it shall be weighed, opened, and stirred 
with a stiff spatula or paddle. The paste must be no more difficult 
to break up and show no more caking than a normal good grade of 
white lead paste. The paste shall be finally thoroughly mixed, 
removed from the container, and the container wiped clean and 
weighed. ‘This weight subtracted from the weight of the original 
package gives the net weight of the contents. A portion of the 
thoroughly mixed paste shall be placed in a clean container and 
the portions for the remaining tests promptly weighed out from it. 

(6) Mrxine with LINSEED Om,.—One hundred grams of the 
paste shall be placed in a cup, and 30 cc of linseed oil added slowly 
with careful stirring and mixing with a spatula or paddle. The 
resulting mixture must be smooth and of good brushing con- 
sistency. 

(c) MOISTURE AND OTHER VOLATILE MatTTER.—Weigh accu- 
rately from 3 to 5 g of the paste into a tared flat-bottomed dish, 
about 5 cm in diameter, spreading the paste over the bottom. 
Heat at 105 to 110° C. for one hour, cool and weigh. Calculate loss 
in weight as percentage of moisture and other volatile matter. 

(d) PERCENTAGE OF PicMENT.—Weigh accurately about 15 g 
of the paste into a weighed centrifuge tube. Add 20 to 30 ce of 
“extraction mixture” (see Reagents), mix thoroughly with a glass 
rod, wash the rod with more of the extraction mixture, and add 
sufficient of the reagent to make a total of 60 cc in the tube. 
Place the tube in the container of a centrifuge, surround with water, 


? A method given by Schaeffer, J., Ind. and Eng. Chem., 6, p. 200 (1914), based on calculation of compo- 
sition after determination of moisture, impurities, total lead, and total zinc oxide, is sometimes used. ‘This 
method requires very accurate determination of Pb and ZnO, since the errors of determination are multi- 
plied by approximately four in making the calculation to PbO and Pbsoa. 


104952°—24 2 


6 Circular of the Bureau of Standards 


and counterbalance the container of the opposite arm with a sim- 
ilar tube or a tube with water. Whirl at a moderate speed 
until well settled. Decant the clear supernatant liquid. Repeat 
the extraction twice with 4o cc of extraction mixture and once 
with 4o cc of ether. After drawing off the ether set the tube in 
a beaker of water at about 80° C. or on top of a warm oven for 10 
minutes, then in an oven at 110 to II 5° C. for two hours. Cool, 
weigh, and calculate the percentage of pigment. 
(e) EXAMINATION OF PicMent.—Grind the pigment from (d) to 
a fine powder, pass through a No. 80 screen to remove any ‘‘skins,”’ 
preserve in a stoppered tube, and examine as under 3 (a), 3(0), 3(d), 
3 (f), 3(9), 3(2), and 3 (2), Laboratory Examination of Dry Pigment. 
({) PREPARATION OF FaTTy Aciws.—To about 25 g of the paste 
in a porcelain casserole add 15 cc of aqueous sodium hydroxide 
(see Reagents), and 75 cc of ethyl alcohol, mix, and heat uncovered 
on a steam bath until saponification is complete (about 1 hour). 
Add 100 ce of water, boil, add sulphuric acid of specific gravity 
1.2 (8 to 10 cc in excess), boil, stir, and transfer to a separatory 
funnel to which some water has been previously added. Draw 
off as much as possible of the acid aqueous layer and PbSO, 
precipitate, wash once with water, then add 50 cc of water and 
so ce of ether. Shake very gently with a whirling motion to 
dissolve the fatty acids in the ether, but not violently, so as to 
avoid forming an emulsion. Draw off the aqueous layer and wash 
the ether layer with one 15 ce portion of water and then with 5 cc 
portions of water until free from sulphuric acid. Then draw off 
completely the water layer. Transfer the ether solution to a dry 
flask, add 25 to 50 g of anhydrous sodium sulphate. Stopper the 
flask and let stand with occasional shaking at a temperature below 
25° C. until the water is completely removed from the ether solu- 
tion, which will be shown by the solution becoming perfectly clear 
above the solid sodium sulphate. Decant this clear solution (if 
necessary through a dry filter paper) into a dry 100 ce Erlenmeyer 
flask. Pass a rapid current of dry air (pass through CaCl, tower) 
into the mouth of the Erlenmeyer flask and heat to a temperature 
below 75° C. on a dry hot plate until the ether is entirely driven 
off. The fatty acids prepared as above should be kept in a stop- 
pered flask and examined at once.* 
3Itis important to follow all of the details since ether generally contains alcohol and after washing 
with water always contains water. It is very difficult to remove water and alcohol by evaporation from 
fatty acids, but the washing of the ether solution and subsequent drying with anhydrous sodium sulphate 


removes both water andalcohol. Ether, in the absence of water and alcohol, is easily removed from fatty 
acids by gentle heat. 


Specification for Basic Sulphate White Lead, Dry and Paste 7 


(g) Test For MINERAL O1L.—Place 10 drops of the fatty acid 
(7) in a 50 cc test tube, add 5 cc of alcoholic soda (see Reagents), 
boil vigorously for 5 minutes, add 40 cc of water, and mix; a clear 
solution indicates that not more than traces of unsaponifiable 
matter are present. If the solution is not clear the oil is not pure 
linseed oil. 

(h) lopine NuMBER oF Farry Acips.—Place a small quantity of 
the fatty acids (f) in a small weighing burette or beaker and weigh 
accurately. ‘Transfer by dropping about 0.15 g (0.10 to 0.20 g) 
to a 50occ bottle having a well-ground glass stopper, or an Erlen- 
meyer flask having a specially flanged neck for the iodine test. 
Reweigh the burette or beaker and determine the amount of sample 
used. Add 1toccof chloroform and whirl the bottle to dissolve the 
sample. Add 1occ of chloroform to each of two empty bottles like 
that used for the sample. Add to each bottle 25 cc of the Hanus 
solution (see Reagents 5) and let stand with occasional shaking 
for one-half hour. Add 10 ce of the 15 per cent potassium iodide 
solution and 100 ce of water, and titrate with standard sodium 
thiosulphate, using starch as indicator. The titration on the two 
blank tests should agree within 0.1 cc. From the difference be- 
tween the average of the blank titrations and the titration on the 
sample and the iodine value of the thiosulphate solution, calculate 
the iodine number of the sample tested. (Iodine number is centi- 
grams of iodine to1 gof sample.) If the iodine number is less than 
170, the oil does not meet the specification. 

(1) COARSE PARTICLES AND “SKINS.’’—Weigh out an amount 
of paste containing 25 g of pigment (see d), add 1oocc of kero- 
sene, wash through No. 325 screen, and weigh the residue as 
in 3 (c). 

5. REAGENTS. 

(2) Acid AMMONIUM ACETATE SOLUTION.—Mix 150 cc of 80 
per cent acetic acid, 100 ce of water, and 95 cc of strong ammo- 
nium (specific gravity 0.90). 

(6) DICHROMATE SOLUTION.—Dissolve 100 g sodium dichro- 
mate (Na,Cr,0,2H,O) or potassium dichromate (K,Cr,O,) in water 
and dilute to 1,000 cc. 

(c) URANYL INDICATOR FOR ZINC TIrRATION.—A 5 per cent 
solution of uranyl nitrate in water or a 5 per cent solution of 
uranyl acetate in water made slightly acid with acetic acid. 

(d) STANDARD PoTASSIUM FERROCYANIDE.—Dissolve 22 g 
of the pure salt in water and dilute to 1,000 cc. To standardize, 


8 Circular of the Bureau of Standards 


transfer about 0.2 g (accurately weighed) of pure metallic zine or 
freshly ignited pure ZnO to a 400 cc beaker. Dissolve in 10 cc 
of HCland 20 cc of water. Drop in a small piece of litmus paper, 
add NH,OH until slightly alkaline, then add HCI until just acid 
and finally add 3 cc of strong HCl. Dilute to about 250 cc with 
hot water and heat nearly to boiling. Run in the ferrocyanide 
solution slowly from a burette with constant stirrmg until a drop 
tested on a white porcelain plate with a drop of the uranyl indica- 
tor shows a brown tinge after standing 1 minute. A blank should be 
run with the same amounits of reagents and water as in the stand- 
ardization. The amount of ferrocyanide solution required for 
the blank should be subtracted from the amounts used in stand- 
ardization and in titration of the sample. The standardization 
must be made under the same conditions of temperature, volume 
and acidity as obtain when the sample is titrated. 

(ec) BARtuM CHLORIDE SoLuTIOoN.—Dissolve 100 g of pure 
crystallized barium chloride in water and dilute to 1,000 cc. 

(f) STANDARD SODIUM THIOSULPHATE SOLUTION.— Dissolve pure 
sodium thiosulphate in distilled water that has been well boiled to 
free it from CO, in the proportion of 24.83 g of crystallized 
sodium thiosulphate to 1,000 cc of the solution. It is best to 
let this solution stand for about two weeks before standardiz- 
ing. Standardize with pure resublimed iodine. (See Treadwell- 
Hall, Analytical Chemistry, vol. 2, 3d ed., p. 646.) This solu- 
tion will be approximately decinormal, and it is best to leave it as 
it is after determining its exact iodine value, rather than to at- 
tempt to adjust it to exactly decinormal strength. Preserve in a 
stock bottle provided with a guard tube filled with soda lime. 

(g) Srarcu SOLUTION.—Stir up 2 to 3 g of potato starch or 5 
g of soluble starch with 100 ce of 1 per cent salicylic acid solu- 
tion, add 300 to 400 cc of boiling water, and boil the mixture until 
the starch is practically dissolved; then dilute to 1 liter. 

(h) EXTRACTION MIXTURE.—Mix 10 volumes ether (ethyl ether), 
6 volumes benzol, 4 volumes methyl alcohol, and 1 volume acetone. 

(1) AguEOUS Soprum HyprOxIDE.—Dissolve 100 g of NaOH 
in distilled water and dilute to 300 cc. | 

(7) PotTasstum IopipE SoLUTION.—Dissolve 150 g of potassium 
iodide free from iodate in distilled water and dilute to 1,000 cc. 

(k) Hanus SoLuTION.—Dissolve 13.2 g of iodine in 1,000 cc 
of glacial acetic acid, 99.5 per cent, which will not reduce chromic 
acid. Add enough bromine to double the halogen content, de- 


Specification for Basic Sulphate White Lead, Dry and Paste 9 


termined by titration (3 cc of bromine is about the proper 
amount). ‘The iodine may be dissolved by the aid of heat, but 
the solution should be cold when the bromine is added. 

(7) Atconotic Soprum MHyproxipE SoLuTion.—Dissolve 
pure sodium hydroxide in 95 per cent ethyl alcohol in the propor- 
tion of about 22 g per 1,000 cc. Letstand ina stoppered bottle. 
Decant the clear liquid into another bottle, and keep well stop- 
pered. This solution should be colorless or only slightly yellow 
when used; it will keep colorless longer if the alcohol is previously 
treated with NaOH (about 80 g to 1,000 cc) kept at about 50°C. 
for 15 days, and then distilled. 


ADDITIONAL COPIES 


OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 

AT 


5 CENTS PER COPY 
Ve 


. 


if, 


3 


s 


v, 


DEPARTMENT OF COMMERCE 


BUREAU OF STANDARDS 
S. W. STRATTON, Director 


CIRCULAR OF THE BUREAU OF STANDARDS 
No. 86 


[2d edition. October 6, 1922] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
TURPENTINE 


(Gum Spirits and Wood Turpentine) 


FEDERAL SPECIFICATIONS BOARD 
STANDARD SPECIFICATION NO. 7 


This specification was officially adopted by the Federal Specifications Board, 
on February 3, 1922, for the use of the Departments and Independent Establish- 
ments of the Government in the purchase of materials covered by it. 


CONTENTS 


Page 

Paes meet Yr cid Sia as seltieek Aes aod ea MO gethn OO I 

2. Detection and removal of separated water...... 2.0... ec cece cece ececceccces 2 

I Re i, os card as Ga ee ads 2 

Pre ermcery Se MettAarION <6. 2. oe, Oe ROR Ee VE Woe! ED 3 

Seen pe Ibiasl? oii Ale. ctr ib hoo Giese teste Be) 
1. GENERAL 


These specifications apply both to the turpentine which is 
distilled from pine oleoresins, commonly known as gum Spirits or 
spirits of turpentine, and to turpentine commonly known as 
wood turpentine, which is obtained from resinous wood, whether 
by steam or by destructive distillation. When ordering under 
these specifications, the purchaser shall specify whether (a) gum 
spirits or (b) wood turpentine is desired. When wood turpentine 
is specified, it may be stated whether steam or destructively 
distilled wood turpentine shall be furnished. 

7788°—22 


2 Circular of the Bureau of Standards 


Turpentine shall be pure and conform to the following require- 
ments: 

APPEARANCE.—Shall be clear and free from suspended matter 
and water. 

CoLor.—Shall be ‘‘standard”’ or better. 

Opor.—Shall be characteristic of the variety of turpentine 
specified and, if desired, shall conform to the odor of the 
sample agreed upon. 


Maximum Minimum 
Specific gravity, 15.5/15:5° C..i). 6s <nenio eae aun ae 0.875 | 0.862 
Refractive index at 20° C, gum spirits................. 1.478 1.468 
Refractive index at 20° C, wood turpentine.............. 1.478 1.465 
Residue after polymerization with 38 N H,SO,: 
Gum spirits— 
Volume. (per Cent) }:..¢240) « pee eine eee ee 20: Feteeey id baa 
Refractive index at 20° C.... 0.05... .25 0205s une] eiee ee 1.500 — 
Wood turpentine— 
Volume (per-Cent)s. 500/500). Pee ae 25> - he Ga eeeens 
Refractive index at 20° C........5...... cds ee ees eT Pen 1.480 | 
Initial boiling point at 760 mm pressure................ 160°C * os fee 
Distilling below 170° C at 760 mm pressure (per cent)...]............, 90 


2. DETECTION AND REMOVAL OF SEPARATED WATER 


Draw a portion by means of a glass or metal container with a 
- removable stopper or top, or with a “‘ thief,’ from the lowest part 
of the container, or by opening the bottom valve of the perfectly 
level tank car. If water is found to be present, draw it all out, 
record the quantity, and deduct it from the total volume of liquid 


delivered. 
3. SAMPLING 


The method of sampling given under (a) should be used when- 
ever feasible. When method (a) is not applicable, method (0), 
(c), or (d) is to be used according to the special conditions that 
obtain. 

(a) While Loading Tank Car or While Filling Containers for 
Shipment.—Samples shall be drawn by the purchaser’s inspector 
at the discharge pipe where it enters the receiving vessel or vessels, 
The‘ composite sample shall be not less than 5 gallons and shall 
consist of small portions of not more than 1 quart each taken at 
regular intervals during the entire period of loading or filling. — 


Specifications for Turpentine 3 


The composite sample thus obtained shall be thoroughly mixed 
and from it three samples of not less than 1 quart each shall be 
placed in clean, dry, glass bottles or tin cans, which must be 
nearly filled with the sample and securely stoppered with new, 
clean corks or well-fitting covers or caps. “These shall be sealed 
and distinctly labeled by the inspector; one shall be delivered to. 
the buyer, one to the seller, and the third held for check in case 
of dispute. 

(6) From Loaded Tank Car or Other Large Vessel.—The com- 
posite sample taken shall be not less than 5 gallons and shall 
consist of numerous small samples of not more than 1 quart each 
taken from the top, bottom, and intermediate points by means 
of a metal or glass container with removable stopper or top. 
This device, attached. to a suitable pole, is lowered to the various 
desired depths, when the stopper or top is removed and the con- 
tainer allowed to fill. The sample thus obtained is handled as 
in (a). 

(c) Barrels and Drums.—Barrels and drums shall be sampled 
aiter gaging contents. Five per cent of the packages in any ship- 
ment or delivery shall be represented in the sample. Thoroughly 
mix the contents of each barrel to be sampled by stirring with a 
clean rod and withdraw a portion from about the center by means 
of a “thief” or other sampling device. The composite sample 
thus obtained shall be not less than 3 quarts, shall consist of equal 
portions of not less than one-half pint from each package sampled, 
and shall be handled asin (a). Should the inspector suspect adul- 
teration, he shall draw the samples from the suspected packages. 

(dq) Small Containers, Cans, Etc., of 10 Gallons or Less.—T'hese 
should be sampled, while filling, ea method (a) whenever possible; 
but in case this is impossible the composite sample taken shall be 
not less than 3 quarts. This shall be drawn from at least five 
packages (from all when fewer), and in no case from less than 
2 per cent of the packages. The composite sample thus taken 
shall be thoroughly mixed and subdivided as in (a). 


4. LABORATORY EXAMINATION 


Samples will, in general, be tested by the following methods; 
but the purchaser reserves the right to apply any additional tests 
or use any available information to ascertain whether the material 
meets the specifications: 

(a) Appearance.—Examine to determine compliance with the 
specifications. 


A Circular of the Bureau of Standards 


(b) Color.—Fill a 200 mm perfectly flat-bottomed colorimeter 
tube, graduated in millimeters, to a depth of from 40 to 50 mm 
with the turpentine to beexamined. Place the tube in a colorim- 
eter and place on or under it a No. 2 yellow Lovibond glass. 
Over or under a second graduated tube in the colorimeter, place 
a No. 1 yellow Lovibond glass and run in the same turpentine 
until the color matches as nearly as possible the color in the first 
tube. Read the difference in depth of the turpentine in the two 
tubes. If this difference is 50 mm or more, the turpentine is 
“standard’’ or better. 

(c) Odor.—Determine’ by comparison with several samples of 
known purity, which have been kept in the dark in completely 
filled, well-stoppered bottles and are free from separated water. 

(d) Specific Gravity Determine at 15. 5/15.5° C, in a pycnom- 
eter accurately standardized and having a capacity of at least 
25 cc, or by any other equally accurate method. 

(e) Refractive Index.—Determine refractive index at 20° C with 
an accurate instrument. When the refractive index is determined 
at any other temperature, the readings obtained shall be corrected 
to 20° C by adding to or by subtracting from the actual reading 
0.00045 for each degree centigrade that the temperature at which 
the determination was made is, respectively, above or below 20° C. 

(f) Distillation —Apparatus.*—C ondenser.—The type of appa- 
ratus (see Fig. 1) adopted by the American Society for Testing Mate- 
rials for the distillation of paint thinners other than turpentine, 
substituting for the thermometer there described? an immersed ther- 
mometer such as is described below, is preferred. In case the 
A.S.’T. M. distillation apparatus is not available, use an ordinary 
straight glass-tube condenser, about 22 inches long, with 16 inches 
in contact with the cooling water. The end of the condenser tube 
should be fitted with an adapter or should be bent down to a 
nearly vertical position, and the tip should be cut off or ground 
down at an acute angle. The tip should extend a short distance 
into the receiving cylinder. 

Flask.—Comparable results can be obtained only by using 
flasks of the same dimensions. ‘The distilling flask used shall be 
the standard Engler flask, as used for petroleum distillation, 
having the following dimensions: Diameter of bulb, 6.5 cm; 
cylindrical neck, 15 cm long, 1.6 cm internal diameter; side or 
vapor tube, 10 cm long, 0.6 cm external diameter, attached to 


ee a ee 


1 Fig. 1. 2A.S. T. M. Standards, p. 607; roz8. 


Specifications for Turpentine 5 


. neck at an angle of 75°, so that when the flask contains its charge 
of 100 ce of oil the surface of the liquid shall be 9 cm below the 
bottom of the junction of the side tube and neck. 

Support for Flask.—Support the flask on a plate of asbestos 
20 cm in diameter, having an opening 4 cm in diameter. in its: 
center, and heat with an open flame. Surround the flask and 
burner with a shield to prevent fluctuation in the temperature of 
the neck of the flask. Or, support the flask in a metal cup, 15 to 
20 cm in diameter, containing high-boiling mineral oil or glycerin 


aD | 


Fic. 1.—Distillation apparatus 


and fitted with a concave cover having in the center a circular 
opening 54 to6 cmin diameter. In all cases take the necessary 
precautions to prevent fluctuation in temperature in the neck of 
the flask. 
Thermometer.—The thermometer used for turpentine distillation 
shall conformi to the following specifications: : 
It shall be graduated from 145° to at least 200° C in 0.2° inter- 
vals. Thermometers graduated above 200° C may be used, pro- 
vided they also comply with the following requirements: Length, 
bottom of thermometer to 175° mark, not more than 8 nor less than 


6 Circular of the Bureau of Standards 


6.5 cm. Length, top of bulb to 145° mark, not less than 1.5 cm. | 


Length, 145 to 175° mark, not more than 6 cm. 

The thermometer shall be made of suitable thermometric glass 
and thoroughly annealed, so that the scale errors will not increase 
after continued heating. | 

The thermometer shall be filled above the mercury with an inert 
gas, with sufficient pressure above the mercury column to prevent 
breaking of the column. It shall have a reservoir at the top, so 
that the pressure will not become excessive at the highest tem- 
perature. 

Every fifth graduation shall be longer than the intermediate 
ones, and the marks shall be numbered at each interval of 5°. 
The graduation marks shall be clear-cut and fine and the number- 
ing clear-cut and distinct. . 

The error at any point on the scale shall not exceed +0.5° CG 
when tested for total immersion of the mercury column. 

Receiving Cylinder.—Collect the distillate in an accurately grad- 
uated so or 100 ce cylinder. The so-called normal or precision 
cylinder of 50 cc capacity, having an internal diameter of 1.5 cm 
and graduated in 0.2 cc, is preferred. If a cylinder with larger 
inside diameter is used, a pasteboard cover should be placed over 
the top and surround the condenser tube. 

OPERATION.—Place 100 ce of the turpentine and several small 
pieces of pumice (or glass) in the distilling flask, fit the thermom- 
eter so that the top of the mercury bulb is level with the bottom 
of the side tube, and the 175° C (347° F) mark is below the cork. 


Place the flask in position on the asbestos board or oil bath and — 


connect with the condenser. Apply the heat cautiously at first, 
and, when distillation begins, regulate the heat so that the tur- 
pentine distills at the rate of not less than 4 nor more than 5 cc 
per minute (approximately two drops per second). The initial 
boiling point is the thermometer reading at the instant when the 
first drop falls from the end of the condenser. Discontinue dis- 
tillation when the temperature reaches 170.0° C (338° F), or an 
equivalent thereof, depending on the atmospheric pressure, as 
outlined below; let the condenser drain and read the percentage 
distilled. 

The percentage distilled below successive selected temperatures 
and the temperature at which each successive 10 ce. distills may 
also be determined, if desired, making the necessary correction 0 
the temperature for variations in atmospheric pressure. _ Ss 


2 a 


Specifications for Turpentine 4 


CORRECTION FOR VARIATION IN ATMOSPHERIC PRESSURE.— 
Since distillation results are comparable only when obtained 
under exactly the same pressure conditions, turpentine shall be 
distilled at that pressure which, at room temperature, is equivalent 
to a pressure of 760 mm of mercury ato°C. Whenever the atmos- 
pheric pressure after correcting to 0° C is other than 760 mm, a 
correction must be made. Since alteration of the pressure in the 
distilling system requires rather complicated apparatus, it is 
simpler to alter the temperature observation points to correspond to 
the prevailing pressure. 

To determine what the atmospheric pressure at the prevailing 
room temperature, or at the temperature of the barometer, would 
be at 0° C, read the barometer and thermometer alongside when 
about to begin distillation. Refer to Table 1, page rz. Under the 
column nearest the observed pressure reading, and on the line 
nearest the observed temperature of the barometer will be found 
the correction which must be subtracted from the observed pres- 
sure reading to obtain the equivalent, or true, reading at 0° C. 

The distilling temperature of turpentine is affected plus (-) or 
minus (—) 0.057° C for each millimeter variation of the barometer 
above or below the normal 760 mm ato° C2 If the barometer 
reading, after correcting to 0° C, is below 760 mm, the turpen- 
tine will distill at a slightly lower temperature than under normal 
pressure. Therefore, the temperature recorded at the beginning 
of distillation (and any others observed during the course of the 
distillation) must be corrected to get its équivalent at normal 
pressure. ‘The final temperature observation point (170° C of the 
specifications) must be altered accordingly to get its equiva- 
lent at the pressure (corrected to 0° C) at which distillation is 
made. 

For example, if the barometer reading, after correcting to 
o°® C, is 750 mm, the correction of the observed initial distilling 
temperature will be 0.057 10=0.6° C approximately. If the 
reading of the thermometer when the turpentine begins to 
distill is 155.6° C, the corrected initial distilling temperature will 
be 155.6°+0.6°=156.2° C. Furthermore, the temperature ob- 
servation point at end of distillation (170.0° C at 760 mm) must 
be altered to the same extent. Since the turpentine is distilling 
0.6° C below what it would at normal pressure, distillation must 


§ Landolt-Bornstein Physikalisch-Chemische Tabellen, Ed. 4, Table 127, p. 43 ce 


8 Circular of the Bureau of Standards 


be discontinued at 0.6° C below the specified limit of 170.0° C to 
determine the percentage distilling below 170.0° C. , 

If the barometer reading corrected to 0° C is above 760 mm, 
subtract the temperature correction from the observed ther- 
mometer reading to determine the initial distilling point, and 
continue distillation to 170.0° C plus the correction to determine 
the percentage distilling below 170.0° C. 

(g) Polymerization.—Place 20 cc of 38 N (equivalent to 100.92 
per cent H,SO,) sulphuric acid in a graduated, narrow-necked 
Babcock flask, stopper, and place in ice water to cool. Add 
slowly, from a pipette, 5 cc of the turpentine to be examined. 
Gradually mix the contents, keeping warm, but being very care- 
ful that the temperature does not rise above 60° C. When the 
mixture no longer warms up on shaking, agitate thoroughly and 
place the flask in a water bath and heat at 60 to 65° C for not 
less than 10 minutes, keeping the contents of the flask thoroughly 
mixed by vigorous shaking for one-half minute each time, six 
times during the period. Do not stopper the flask after the 
turpentine has been added, as it may explode. Cool to room 
temperature, fill the flask with concentrated sulphuric acid until 
the unpolymerized oil rises into the graduated neck and centri- 
fuge from four to five minutes at not less than 1200 r. p. m., or 
for 15 minutes at 900 r. p. m., or allow to stand, lightly stop- 
pered, for 12 hours. Calculate the percentage, note the consist- 
ency and color, and determine the refractive index (at 20° C) 
of the unpolymerized residue. The consistency should be viscous 
and the color straw or darker. 

REAGENT FOR TESTING.—In a weighed glass-stoppered bottle 
(the regular 2'%4-liter acid bottle is of a convenient size) mix 
ordinary concentrated sulphuric acid (sp. gr. 1.84) with fuming 
sulphuric acid. If the fuming acid used contains 50 per cent 
excess SO,, the ratio of one part, by weight, of the former to 
three-fourths of a part, by weight, of the latter will give a mix- 
ture slightly stronger than the required strength. To determine 
‘the exact strength of this mixture in terms of H,SO,, weigh 
exactly, in a weighing pipette of about 10 ce capacity, approxi- 
mately 20 g of the acid. Allow it to flow down the sides of the 
neck into a 1o00-cec volumetric flask containing about 200 ce of 
distilled water. When the pipette has drained, wash all traces of 
the acid remaining in the pipette into the flask, taking precau- 
tions to prevent loss of SO,, and make up to the mark. Titrate 


Specifications for Turpentine 9 


20-cc portions, drawn from a burette, against half normal alkali. 
Calculate the concentration in terms of the percentage of H,SO, 
in the sample taken. 

In the same way determine the percentage of H,SO, in the 
stock of ordinary concentrated acid (sp. gr. 1.84). From these 
data calculate the quantity of the 
latter which must be added to the 


quantity of mixed acid in the 
weighed bottle to bring it to a 
concentration, in terms of H,SO,, of 
100.92 per cent. 

After adjusting the concentration 
by the addition of the ordinary 
sulphuric acid, thoroughly shake the 
bottle of mixed acid and again de- 
‘termine its concentration. The al- 
lowable variation is + 0.05 per cent 
HpO).s Eimally as a check run a 
polymerization test on gum turpen- 
tine known to be pure. The residue 
should fall below 2 per cent. 

Special precautions must be taken 
to prevent dilution of this acid by 
the absorption of atmospheric mois- 
ture. The arrangement shown in 
Fig. 2 is most suitable for storing 
and delivering measured quantities 
of this reagent. 

With the three-way stopcocks A 
and B in the position shown, acid is 
siphoned into the pipette P, the dis- 
» placed air passing into R. To empty 
the pipette, A and B are turned to 
the position shawn by the broken lines, air passing in at a. The 
acid adhering to the walls of the pipette dries this air so that 
when it passes into R on again filling the pipette there is no 
accumulation of moisture in the acid remaining in the reser- 
voir. If such arrangement is not to be had, the acid should be 
kept in well-fitting glass-stoppered bottles of not more than one- 
_ half liter capacity. 


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DEPARTMENT OF COMMERCE. 
BUREAU OF STANDARDS. 


S. W. STRATTON, Director. 


CIRCULAR OF THE BUREAU OF STANDARDS. 
No. 87. 


[2d edition. Issued July 3, 1922.] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
ZINC OXIDE, DRY AND PASTE. 


FEDERAL SPECIFICATIONS BOARD. 
STANDARD SPECIFICATION No. 8. 


‘This Specification was officially adopted by the Federal Specifications Board on 
February 3, 1922, for the use of the Departments and Independent Establish- 
ments of the Government in the purchase of materials covered by it. 


CONTENTS. 
Page. 
NE Be cide ain gS woe Sosa, so sibge dpe td UV aL Oeeh Deon I 
eR MMM ee OT Tae oe ois oc eres ae Mate Sele tp OVEN ERS OE OU ee a 2 
3. Laboratory examination of dry pigment............... BME, UD LN se ER OO 3 
Ppaeeoe yeexaniisation Of paste. (. iss 64 a eas dyaet as <a ebb vhs empire eit 4 
MAM ONNED Cee ie a dd pn Son axis 2 8s Se PER Se RO RO eS 7 


1. GENERAL. 


Zinc oxide may be ordered in the form of dry pigment or paste 
_ ground in linseed oil. Purchases shall be made on the basis of 
met weight. 

mT he pigment may be American process zinc oxide, made direct 
from the ore, or French process zinc oxide, made from spelter. 
The contract shall state which kind is desired. 

‘The color and color strength when specified shall be equal to 
samples mutually agreed upon by buyer and seller. 

109842°—22 


? 


2 Circular of the Bureau of Standards 


The pigment shall meet the following requirements: 
Maximum.| Minimum. 


Coarse particles retained on Standard No. 325 screen 


Per cent. | Percent. | Percent. | Per cent. 
99 


PANG OTING oes Fic Unis 2 Rw EL ae he hl EN ES eer ae eee ate een 98 righ eeowaee 
Retel CCG ness we ceathas token reprise Ama ae OF 2.15) eee O.3 i550 eee 
Total impurities, including moisture................... Be OC REA eee Ode tae 


The paste shall be made by thoroughly grinding the above 
pigment with pure raw or refined linseed oil. The paste shall 
not cake in the container and shall break up readily in oil to 
form a smooth paint of brushing consistency. 

The paste shall consist of: 


Pigment, ic}. casivwidiy Salar argent sh wsliepiale ste siya tunel tematic 

TAneeed Ol. Via 5h re bee ay me aga vinsieds tsa Ns cans te oy Crk 18 14 
Coarse particles and ‘‘skins’’ (total residue left on No. 325 screen based on pigment) | — 1. Sta ngy tog thes 
Moisture and other volatile matter... oo... ee... coca cc so caer sae eee O).5 Nc oeee 


Norte.—Deliveries will, in general, be sampled and tested by the following methods, but the purchaser 
reserves the right to use any additional available information to ascertain whether the material meets the 
specification. 


2. SAMPLING. 


It is mutually agreed by buyer and seller that a single package 
out of each lot of not more than 1,000 packages shall be taken as 
representative of the whole. 

With the dry pigment, this package is to be opened by the in- 
spector and a sample of not less than 5 pounds taken at random 
from the contents and sent to the laboratory for test. When 
requested, a duplicate sample may be taken from the same pack- 
age and delivered to the seller, and the inspector may take a third 
sample to hold for test. in case of dispute. | 

With the paste, whenever possible, an original unopened con- 
tainer shall be sent to the laboratory; and when this is for any 
reason not done, the inspector shall determine by thoroughly test- 
ing with a paddle or spatula whether the material meets the 
requirement regarding not caking in the container. (See 4 (a).) 
After assuring himself that the paste is not caked in the can, the 


Spectfication for Zinc Oxide, Dry and Paste 3 


inspector shall draw a sample of not less than 5 pounds of the 
thoroughly mixed paste, place it in a clean, dry metal or glass 
container which must be filled with the sample, closed with a tight 
cover, sealed, marked, and sent to the laboratory for test with the 
inspector’s report on caking in container. 


3. LABORATORY EXAMINATION OF DRY PIGMENT. 


(a) Cotor.—Take 5 g of the sample, add 1.5 cc of linseed oil, 
rub up on a stone slab or glass plate with a flat-bottomed glass or 
stone pestle or muller to a uniform smooth paste. Treat in a 
similar manner 5 g of the standard zinc oxide. Spread the two 
pastes side by side on a clear colorless glass plate and compare the 
colors. If the sample is as white as or whiter than the “‘ standard,” 
it passes this test. If the “standard” is whiter than the sample, 
the material does not meet the specification. 

(6) CoLoR STRENGTH.—Weigh accurately 0.01 g of lampblack, 
place on a large glass plate or stone slab, add 0.2 cc of linseed oil 
and rub up with a flat-bottomed glass pestle or muller, than add 
exactly 10 g of the sample and 2.5 cc of linseed oil, and grind with 
a circular motion of the muller 50 times; gather up with a sharp- 
edged spatula and grind out twice more in a like manner, giving 
the pestle a uniform pressure. Treat another 0.01 g of the same 
lampblack in the same manner except that 10 g of standard zine 
oxide is used instead of the 10 g of the sample. Spread the two 
pastes side by side on a glass microscope slide and compare the 
colors. If the sample is as light as or lighter in color than the 
“standard,” it passes this test. If the ‘‘standard”’ is lighter in 
color than the sample, the material does not meet the specification. 

(c) COARSE PARTICLES.'—Dry in an oven at 105 to 110° C. a 
325 screen, cool and weigh accurately. Weigh 10g of the sample; 
dry at 100° C., transfer to a mortar, add 100 cc kerosene, thor- 
oughly mix by gentle pressure with a pestle to break up all lumps, 
wash with kerosene through the screen, breaking up all lumps, 
but not grinding. After washing with kerosene until all but the 
particles which are too coarse to pass the screen have been washed 
through, wash all kerosene from the screen with ether or petro- 
leum ether, heat the screen for one hour at 105 to 110° C., cool and 
weigh. 


1 For a general discussion of screen tests of pigments and data regarding many pigments on the market, 
see Circular No. 148 of the Educational Bureau, Scientific Section, Paint Manufacturers’ Association of 
the United States. 


4 Circular of the Bureau of Standards 


(d) QUALITATIVE ANALYsIs.—Test for matter insoluble in hy- 
drochloric acid, for lead, calcium, etc., by regular methods of 
qualitative analysis. 

(e) Zinc OxipE.—With samples free from impurities (see (d)), 
ignite a weighed sample and calculate the residue as ZnO. With 
samples containing impurity, proceed as follows: Weigh accu- 
rately about 0.25 g, transfer to a 400 cc beaker, moisten with 
alcohol, dissolve in ro cc of hydrochloric acid and 20 cc of water 
and titrate with standard potassium ferrocyanide following the 
procedure used in standardizing this reagent. (See 5(2).) 

(f) Tora, SuLpHUR.—Weigh accurately about 10 g of the 
sample. Moisten with afew drops of alcohol, add 5 cc of bromine 
water (saturated solution of bromine), then concentrated hydro- 
chloric acid in excess, boil to expel bromine, and dilute to about 
100 cc. (Material complying with the specification should all go 
into solution; if insoluble matter remains, filter and examine by 
appropriate methods.) Make alkaline with ammonia, then just 
acid with hydrochloric acid, heat to boiling and add about 10 cc 
of hot barium chloride solution. (See Reagents.) Let stand 
several hours (overnight), filter on a weighed Gooch crucible, 
wash thoroughly with hot water, dry, ignite, cool, and weigh the 
BaSO,. . Calculate to S (BaSO, X 0.1373 =5); 


4. LABORATORY EXAMINATION OF PASTE. 


(a) CAKING IN CONTAINER.—When an original package is re- 
ceived in the laboratory, it shall be weighed, opened, and stirred 
with a stiff spatula or paddle. The paste must be no more difficult 
to break up and show no more caking than a normal good grade 
of zinc oxide paste. ‘The paste shall be finally thoroughly mixed, 
removed from the container, the container wiped clean, and 
weighed. This weight subtracted from the weight of the original 
package gives the net weight of the contents. A portion of the 
thoroughly mixed paste shall be placed in a clean container and 
the portions for the remaining tests promptly weighed out. 

(0) MIxING witH LINSEED O1,.—One hundred grams of the 
paste shall be placed in a cup, 35 cc of linseed oil added slowly 
with careful stirring and mixing with a spatula or paddle. The 
resulting mixture must be smooth and of .good brushing con- 
sistency. 

(c) MOISTURE AND OTHER VOLATILE MATTER.—Weigh accu- 
rately from 3 to 5 g of the paste into a tared flat-bottomed dish, 
about 5 cm in diameter, spreading the paste over the bottom. 


Specification for Zinc Oxide, Dry and Paste 5 


Heat at 105 to 110° C. for one hour, cool, and weigh. Calculate 
loss in weight as percentage moisture and other volatile matter. 

(dq) PER Cent PicMENT.—Weigh accurately about 15 g of the 
paste into a weighed centrifuge tube. Add 20 to 30 cc of “‘ex- 
traction mixture’’ (see Reagents), mix thoroughly with a glass 
rod, wash the rod with more of the extraction mixture, and add 
sufficient of the reagent to make a total of 60 cc in the tube. 
Place the tube in the container of a centrifuge, surround with 
water, and counterbalance the container of the opposite arm with 
a similar tube or a tube with water. Whirl at a moderate speed 
until clear. Decant the clear supernatant liquid. Repeat the 
extraction twice with 40 cc portions of extraction mixture, and 
once with 40 cc of ether. After drawing off the ether, set the 
tube in a beaker of water at about 80° C. or on top of a warm 
oven for 10 minutes, then in an oven at 110 to 115° C. for 2 hours. 
Cool, weigh, and calculate percentage of pigment. 

(e) EXAMINATION OF PIGMENT.—Grind the pigment from (d) 
to a fine powder, pass through a No. 80 screen to remove any 
‘“skins,’’ preserve in a stoppered tube and apply tests 3 (d), (e), 
and (f). If required, apply tests 3 (a) and (b) in comparison with 
a portion of pigment extracted from the standard paste in exactly 
the same manner as in extracting the sample. 

(f) PREPARATION OF Fatry Acips.—To about 25 g of the paste 
in a porcelain casserole add 15 cc aqueous sodium hydroxide (see 
Reagents), and 75 cc of ethyl alcohol, mix and heat uncovered on 
a steam bath until saponification is complete (about one hour). 
Add 100 cc water, boil, add an excess of sulphuric acid of specific 
gravity 1.2 (8 to 10 ce will usually suffice), boil, stir, and transfer 
to a separatory funnel to which some water has been previously 
added. Draw off as much as possible of the acid aqueous layer, 
wash once with water; then add 50 cc of water and 50 cc of ether. 
Shake very gently with a whirling motion to dissolve the fatty 
acids in the ether, but not violently, so as to avoid forming an 
emulsion. Draw off the aqueous layer and wash the ether layer 
with one 15 cc portion of water and then with 5 cc portions of 
water until free from sulphuric acid. Then draw off completely 
the water layer. ‘Transfer the ether solution to a dry flask, and 
add 25 to 50 g of anhydrous sodium sulphate. Stopper the flask 
and let stand with occasional shaking at a temperature below 25° 
C. until the water is completely removed from the ether solution, 
which will be shown by the solution becoming perfectly clear 


6 Circular of the Bureau of Standards 


above the solid sodium sulphate. Decant this clear solution (if 
necessary through a dry filter paper) into a dry 100 cc Erlenmeyer 
flask. Passa rapid current of dry air (pass through CaCl, tower) 
into the mouth of the Erlenmeyer flask and heat to a temperature 
below 75°C. ona dry hot plate until the either is entirely driven off. 

NorTEe.—It is important to follow all of the details, since ether generally contains 
alcohol and after washing with water always contains water. It is very difficult 
to remove water and alcohol by evaporation from fatty acids, but the washing of the 
ether solution and subsequent drying with anhydrous sodium sulphate removes both 


water and alcohol. Ether, in the absence of water and alcohol, is easily removed 
from fatty acids by gentle heat. 


The fatty acids prepared as above should be kept in a stoppered 
flask and examined at once. 

(g) TEST FOR MINERAL OIL, AND OTHER UNSAPONIFIABLE Mat- 
TER.—Place 10 drops of the fatty acid (f) in a 50 cc test tube, 
add 5 cc of alcoholic soda (see Reagents), boil vigorously for 5 
minutes, add 40 ce of water, and mix; a clear solution indicates 
that not more than traces of unsaponifiable matter are present. 
If the solution is not clear, the oil is not pure linseed oil. 

(h) IopINE NUMBER oF Farry Acips.—Place a small quantity 
of the fatty acids (f) in a small weighing burette or beaker. 
Weigh accurately. Transfer by dropping about 0.15 g (0.10 to 
0.20 g) to a 500 cc bottle having a well-ground glass stopper, or 
an Erlenmeyer flask having a specially flanged neck for the iodine 
test. Reweigh the burette or beaker and determine the amount 
of sample used. Add 1occ of chloroform. Whirl the bottle to 
dissolve the sample. Add ro ce of chloroform to two empty 
bottles like that used for the sample. Add to each bottle 25 cc of 
the Hanus solution (see Reagents) and let stand, with occasional 
shaking, for one-half hour. Add 10 cc of the 15 per cent potas- 
sium-iodide solution and 100 cc of water, and titrate with standard 
sodium thiosulphate, using starch as indicator. ‘The titrations on 
the two blank tests should agree within 0.1 ec. From the differ- 
ence between the average of the blank titrations and the titration 
on the sample and the iodine value of the thiosulphate solution, 
calculate the iodine number of the sample tested. (Iodine 
number is centigrams of iodine to 1 g of sample.) If the iodine 
number is less than 170, the oil does not meet the specification. 

(2) COARSE PARTICLES AND ‘‘SKINS.”—Weigh an amount of 
paste containing 10 g of pigment (see 4 (d)), add kerosene, and 
wash through a No. 325 screen asin 3 (c). ‘The residue is reported - 
as ‘‘Coarse particles and skins.’’ 


Spectfication for Zinc Oxide, Dry and Paste 7 
5. REAGENTS. 


(a) EXTRACTION MIxTURE.— 

10 volumes ether (ethyl ether). 
6 volumes benzol. 
4 volumes methyl alcohol. 
I volume acetone. 

(6) AguEOous Soprum HyproxmpE.—Dissolve 100 g sodium 
hydroxide in distilled water and dilute to 300 ce. 

(c) STANDARD Sopium ‘THIOSULPHATE SoLUTION.—Dissolve 
pure sodium thiosulphate in distilled water that has been well 
boiled to free it from carbon dioxide, in the proportion of 24.83 g 
crystallized sodium thiosulphate to 1,000 cc of the solution. It is 
best to let this solution stand for about two weeks before stand- 
ardizing. Standardize with pure resublimed iodine. (See Ana- 
lytical Chemistry, Treadwell-Hall, vol. 11, 3d ed., p- 646.) This 
solution will be approximately decinormal, and it is best to leave 
it as it is after determining its exact iodine value rather than to 
attempt to adjust it to exactly decinormal. Preserve in a stock 
bottle provided with a guard tube filled with soda lime. 

(d) STaRcH SOLUTION.—Stir up 2 to 3 g of potato starch or 
5 g soluble starch with 100 cc of 1 per cent salicylic acid solution, 
add 300 to 400 cc boiling water, and boil the mixture until the 
starch is practically dissolved, then dilute to 1 liter. 

(e) Porasstum IopIpE SoLUTION.—Dissolve 150 g of potassium 
iodide free from iodate in distilled water and dilute to 1,000 cc. 

(/) Hanus SoLution.—Dissolve 13.2 g of iodine in 1,000 cc 
of 99.5 per cent glacial acetic acid which will not reduce chromic 
acid. Add enough bromine to double the halogen content, 
determined by titration (3 cc of bromine is about the proper 
amount). The iodine may be dissolved by the aid of heat, but 
the solution should be cold when the bromine is added. 

(g) ALCOHOLIC Soprum HyproxIpE SoLuTION.—Dissolve pure 
sodium hydroxide in 95 per cent ethyl alcohol in the proportion 
of about 22 g per 1,000 cc. Let stand in a stoppered bottle. 
Decant the clear liquid into another bottle and keep well stop- 
pered. This solution should be colorless or only slightly yellow 
when used, and it will keep colorless longer if the alcohol is pre- 
viously treated with sodium hydroxide (about 80 g to 1,000 cc), 
kept at about 50° C. for 15 days and then distilled. 


8 Circular of the Bureau of Standards 


(hk) URANYL INDICATOR FOR ZINC TiTRATION.—A 5 per cent 
solution of uranyl nitrate in water or a 5 per cent solution of © 
uranyl acetate in water made slightly acid with acetic acid. 

(i) SraANDARD PotasstuM FERROCYANIDE.—Dissolve 22 g of 
the pure salt in water and dilute to 1,000 cc. To standardize 
transfer about 0.2 g (accurately weighed) of pure metallic zine 
or freshly ignited pure zinc oxide to a 400 cc beaker. Dissolve in 
10 cc hydrochloric acid and 20 cc water. Drop in a small piece 
of litmus paper, add ammonium hydroxide until slightly alkaline, 
then add hydrochloric acid until just acid, and then add 3 cc 
strong hydrochloric acid. Dilute to about 250 cc with hot water 
and heat nearly to boiling. Run in the ferrocyanide solution 
slowly from a burette with constant stirring until a drop tested 
on a white porcelain plate with a drop of the uranyl indicator 
shows a brown tinge after standing one minute. A blank should 
be run with the same amounts of reagents and water as in the 
standardization. The amount of ferrocyanide solution required 
for the blank should be subtracted from the amounts used in 
standardization and in titration of the sample. . The standardiza- 
tion must be made under the same conditions of temperature, 
volume, and acidity as obtain when the sample is titrated. 

(7) Bartum CHLORIDE SOLUTION.—Dissolve 100 g of pure crys- 
tallized barium chloride in water and dilute to 1,000 cc. ig 


ADDITIONAL COPIES 
OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 
AT 
5 CENTS PER COPY 


Vv 


WASHINGTON ; GOVERNMENT PRINTING OFFICE ; 1922 


DEPARTMENT OF COMMERCE. 
BUREAU OF STANDARDS. 


S. W. STRATTON, Director. 


CIRCULAR OF THE BUREAU OF STANDARDS. 
No. 88. 


[2d edition. Issued July 3, 1922.] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
LEADED ZINC OXIDE, DRY AND PASTE. 


FEDERAL SPECIFICATIONS BOARD. 
STANDARD SPECIFICATION NO. 9. 


ae 
This Specification was officially adopted by the Federal Specifications: Board on 
February 3, 1922, for the use of the Departments and Independent Establish- 


ments of the Government in the purchase of materials covered by it. 


CONTENTS. 


Page 

RS STI Bein li a I 

2, Sampling... . 24 EE tS a rr rt ee, Be 2 

3- Laboratory examination of dry pigment.............000 00 ccc cece ccc eeeeee. 3 

We meen y emmteaatigay Of paste nied, (05). 3. 621 iui vaos idle: e.. 4 

5. Reagents....... ioe hine, pel Lo. auivenine. oan, 7 
1. GENERAL. 


Leaded zine oxide, frequently known as leaded zinc, consists 
of zinc oxide and varying amounts of lead compounds. It may 
be ordered in the form of dry pigment or paste ground in linseed 
oil. Purchases shall be made on the basis of net weight. 

The pigment may be high-leaded zinc oxide or low-leaded zinc 
oxide. ‘The contract shall state which kind is desired. ‘The color 
and color strength when specified shall be equal to samples mutu- 
ally agreed upon by buyer and seller. 


*  106489°—24 « 


2 Circular of the Bureau of Standards 


The pigment shall meet the following requirements: 


Maximum.) Minimum, 


eee 


Coarse particles retained on Standard No. 325 screen .-.-------------------+++7"°> 1:0 lice nae e 
en mean tne ernis yl 


High-leaded. Low-leaded. 


Maximum. | Minimum. | Maximum. Minimum. 


pian oe ops 


; Per cent. | Percent. | Percent. | Per cent. 
Zinc oxide (ZnO). . Looe Sa ee LE oS - eS Te aes ee 60° eaten ss ecu 93 
Water soluble salts. .......------------@--+--2-2 ctr 1,0 [Sites TO ae ae 
Total impurities, including MOSUL ss: <<a sks ees sen se 1.5)\sisa Se eeeees 1 ee Pe Rae ee 


The balance to be normal or basic lead sulphate. 

The paste shall be made by thoroughly grinding the above pig- 
ment with pure raw or refined linseed oil. The paste shall not 
cake in the container and shall break up readily in oil to form a 
smooth paint of brushing consistency. The paste shall consist of: 


Meximum.| Minimum. 


Per cent. | Per cent. 
88.0 me 


Pigmient |... . jscsnnsees choses -stee oo sina dram beset oped i> ee nese ae oe 

Linseed Ol... -c-ccn- cco cccn ce weet ewes cee bnncn nec et eine bse 50 ee ee 12.0 
Moisture and other volatile matter. ...--.-----------+-----++-- proto (i Rise Ripa Seno ESS 
Coarse particles and “‘skins”’ (total residue left on No. 325 screen based on pigment) ese 1 a (ees “erst 


Note.—Deliveries will, in general, be sampled and tested by the following methods, but the pur- 


chaser reserves the right to use any additional available information to ascertaim whether the material 
meets the specification. , 


2. SAMPLING. S > 


It is mutually agreed by buyer and seller that a single package 
out of each lot of not more than 1,000 packages shall be taken as 
representative of the whole. ; 

With the dry pigment, the package’ is to be opened by the in- 
spector and a sample of not less than 5 pounds taken at random 
from the contents and sent to the laboratory for test. 

With the paste, whenever possible, an original unopened con- 
tainer shall be sent to the laboratory, and when this is for any 
reason not done, the inspector shall determine, by thorough 
testing with a paddle or spatula, whether the material meets the 
requirement regarding not caking in the container. (See 4 (a.) 
After assuring himself that the paste is not caked in the con- 
tainer, the inspector shall draw a sample of not less than 5 pounds 
of the thoroughly mixed paste, place it in a clean dry metal or 
glass container, which must be filled with the sample, closed with 


Specification for Leaded Zinc Oxide, Dry and Paste 3 


a tight cover, sealed, marked, and sent to the laboratory for test 
with the inspector’s report on caking in container. 

When requested, a duplicate sample may be taken from the 
same package and delivered to the seller, and the inspector may 
take a third sample to hold for test in case of dispute. 


3. LABORATORY EXAMINATION OF DRY PIGMENT. 


(a) CoLtor.—Take 5 g of the sample, add 1.5 cc of linseed oil, 
rub up on a stone slab or glass plate with a flat-bottomed glass 
or stone pestle or muller to a uniform smooth paste. ‘Treat in 
a similar manner 5 g of the standard leaded zinc oxide. Spread 
the two pastes side by side on a clear colorless glass plate and 
compare the colors. If the sample is as white or whiter than the 
“standard,” it passes this test. If the ‘‘standard’’ is whiter 
than the sample, the material does not meet the specification. 

(6) CoLoR STRENGTH.—Weigh accurately 0.01 g of lampblack, 
place on a large glass plate or stone slab, add 0.2 cc of linseed oil, 
and rub up with a flat-bottomed glass pestle or muller; then add 
exactly 10 g of the sample and 2.5 cc of linseed oil, and grind 
with a circular motion of the muller 50 times; gather up with a 
sharp-edged spatula and grind out twice more in a like manner, 
giving the pestle a uniform pressure. ‘reat another 0.01 g of 
the same lampblack in the same manner, except that 10 g of 
standard leaded zinc oxide is used instead of the 10 g of the sam- 
ple. Spread the two pastes side by side on a glass microscope 
slide and compare the colors. If the sample is as light as or lighter 
in color than the ‘‘standard,’’ it passes this test. Ifthe “‘standard”’ 
is lighter in color than the sainple, the material does not meet 
the specification. 

(c). COARSE PARTICLES.'"—Dry in an oven at 105° to 110° C. 
a 325 screen, cool and weigh accurately. Weigh 10 g of the 
sample; dry at 1oo° C., transfer to a mortar, add 100 cc kero- 
sene, thoroughly mix by gentle pressure with a pestle to break up 
all lumps, wash with kerosene through the screen, breaking up all 
lumps, but not grinding. After washing with kerosene until all 
but the particles which are too coarse to pass the screen have been 
washed through, wash all kerosene from the screen with ether or 
petroleum ether, heat the screen for one hour at 105° to 110°C., 
cool and weigh. 4 
1 For a general discussion of screen tests of pigments and data regarding many pigments on the market, 


see Circular No. 148 of the Educational Bureau, Scientific Section, Paint Manufacturers’ Association of 
the U.S. 


4 Circular of the Bureau of Standards 


(d) QUALITATIVE ANALYsSIS.—Test for matter insoluble in hydro- 
chloric acid, lead, calcium, carbon dioxide, etc., by regular methods 
of qualitative analysis. 

(e) MoIstuRE.—Place 1 g of the sample in a wide-mouth short 
weighing tube provided with a glass stopper. Heat with stopper 
removed for two hours at a temperature between 105 and 110° C. 
Insert stopper, cool, and weigh. Calculate loss in weight as 
moisture. | 

(f) WATER SOLUBLE SaLts.—To 10 g of pigment in a 500 cc 
volumetric flask, add 200 cc of water, boil for five minutes, 
nearly fill the flask with hot water, allow to cool, fill to mark, mix, 
filter through a dry paper, discard the first 50 ce of filtrate, 
transfer 100 cc of the filtrate (corresponding to 2 g of sample) 
to a weighed dish, evaporate to dryness, heat for one hour in an 
oven at 105 to 110° C., cool, and weigh, calculate to percentage 
of water soluble salts. 

(g) ZINC OxIDE.— Weigh accurately about 0.3 g of the pigment, 
transfer to a 400 ce beaker, add 30 cc of hydrochloric acid 
(1 :2), boil for two or three minutes, add 200 ce of water and 
a small piece of litmus paper; add ammonium hydroxide until 
slightly alkaline, render just acid with hydrochloric acid, then add 
3 ce of strong hydrochloric acid, heat nearly to boiling, and 
titrate with standard potassium ferrocyanide as in standardizing 
the solution. (See Reagents 5 (d).) Calculate total zinc as ZnO. 

(h) CALCULATIONS.—If, as will be the case with material com- 
plying with the specification, no metals but zine and lead are 
found by qualitative tests, add the percentage of ZnO, moisture, 
and water soluble salts and subtract the sum from 100. Call the 
remainder ‘‘normal and basic lead sulphate.”’ 


4. LABORATORY EXAMINATION OF PASTE. 


(2) CAKING IN ConTAINER.—When an original package is re- 
ceived in the laboratory, it shall be weighed, opened, and stirred 
with a stiff spatula or paddle. ‘The paste must be no more diffi- 
cult to break up and show no more caking than a normal good 
grade of leaded-zinc oxide paste. The paste shall be finally 
thoroughly mixed, removed from the container, the container 
wiped clean, and weighed. This weight subtracted from the 
weight of the original package gives the net weight of the con- 
tents. A portion of the thoroughly mixed paste shall be placed 
in a clean container and the portions for the remaining tests 
promptly weighed out. 


Specification for Leaded Zinc Oxide, Dry and Paste 5 


(6) Mrxine wiry LINSEED O1L.—One hundred grams of the paste 
shall be placed in a cup, 35 ce of linseed oil added slowly with 
careful stirring and mixing with a spatula or paddle, the resulting 
mixture must be smooth and of good brushing consistency. 

(c) MOISTURE AND OTHER VOLATILE MaTTER.—Weigh accu- 
rately from 3 to 5 g of the paste into a tared flat-bottomed dish 
about 5 cm in diameter, spreading the paste over the bottom. 
Heat at 105 to 110° C. for one hour, cool, and weigh. Calculate 
loss in weight as percentage of moisture and other volatile matter. 

(d) PERCENTAGE OF PIGMENT.—Weigh accurately about 15 ¢ 
of the paste into a weighed centrifuge tube. Add 20 to 30 cc 
“extraction mixture’’ (see Reagents), mix thoroughly with a glass 
rod, wash the rod with more of the extraction mixture, add suffi- 
cient of the reagent to make a total of 60 cc in the tube. Place 
the tube in the container of a centrifuge, surround with water, 
and counterbalance the container of the opposite arm with a 
similar tube or a tube with water. Whirl at a moderate speed 
until clear. Decant the clear supernatant liquid. Repeat the 
extraction twice with 4o cc of extraction mixture, and once with 
40 cc of ether. After drawing off the ether, set the tube in a 
beaker of water at about 80° C. or on top of a warm oven for 10 
minutes, then in an oven at 110 to 115° C. for two hours. Cool, 
weigh, and calculate percentage of pigment. 

(¢) EXAMINATION OF PiGMENT.—Grind the pigment from (d) 
to a fine powder, pass through a No. 80 screen to remove any 
‘“skins,’’ preserve in a stoppered tube, and apply tests 3 (d), (f), 
(g), and (h). If required, apply tests 3 (a) and (6) in comparison 
with a portion of pigment extracted from the standard paste in 
exactly the same manner as in extracting the sample. 

(7) PREPARATION OF Farry Acips.—To about 25 g of the 
paste in a porcelain casserole, add 15 cc of aqueous sodium hy- 
droxide (see Reagents) and 75 cc of ethyl alcohol; mix, and heat 
uncovered on a steam bath until saponification is complete (about 
one hour). Add 100 cc of water, boil, add sulphuric acid of 
specific gravity 1.2 (8 to 10 cc in excess); boil, stir, and trans- 
fer to a separatory funnel, to which some water has been pre- 
viously added. Draw off as much as possible of the acid aqueous 
layer and lead sulphate precipitate, wash once with water, then 
add 50 cc of water and 50 cc of ether. Shake very gently with 
a whirling motion to dissolve the fatty acids in the ether, but 
not violently, so as to avoid forming an emulsion. Draw off the 


6 Circular of the Bureau of Standards 


aqueous layer and wash the ether layer with one 15 cc portion of 
water and then with 5 ce portions of water until free from sul- 
phuric acid. Then draw off completely the water layer. Transfer 
the ether solution to a dry flask, add 25 to 50 g. of anhydrous 
sodium sulphate. Stopper the flask and let stand with occa- 
sional shaking at a temperature below 25° C. until the water is 
completely removed from the ether solution, which will be shown 
by the solution becoming perfectly clear above the solid sodium 
sulphate. Decant this clear solution (if necessary, through a dry 
filter paper) into a dry “1oo cc Erlenmeyer flask. Pass a rapid 
current of dry air (pass through CaCl, tower) into the mouth of the 
Erlenmeyer flask and heat to a temperature below 75° C. on a dry 
hot plate until the ether is entirely driven off. 

Novte.—It is important to follow all of the details, since ether generally contains ~ 
alcohol and after washing with water always contains water. It is very difficult 
to remove water and alcohol by evaporation from fatty acids, but the washing of the 
ether solution and subsequent drying with anhydrous sodium sulphate removes both 
water and alcohol. Ether, in the absence of water and alcohol, is easily removed 
from fatty acids by gentle heat. 

The fatty acids prepared as above should be kept in a stoppered 
flask and examined at once. | 

(g) Test FOR MINERAL OI, AND OTHER UNSAPONIFIABLE MAT- 
TER.—Place 10 drops of the fatty acid (f) in a 50 cc test tube, add 
5 cc of alcoholic soda (see Reagents), boil vigorously for five 
minutes, add 4o cc of water and mix; a clear solution indicates 
that not more than traces of unsaponifiable matter are present. 
If the solution is not clear, the oil is not pure linseed oil. 

(hk) IlopInE NUMBER oF Farry Acrps.—Place a small quantity 
of the fatty acids (/) in a small weighing burette or beaker. Weigh 
accurately. Transfer by dropping about 0.15 g (0.10 to 0.20 g) 
to a 500 cc bottle having a well-ground glass stopper or an Erlen- 
meyer flask having a specially flanged neck for the iodine test. 
Reweigh the burette or beaker and determine the amount of sample 
used. Add soccof chloroform. Whirl the bottle to dissolve the 
sample. Add ro cc of chloroform to two empty bottles like that 
used for the sample. Add to each bottle 25 cc of the Hanus solu- 
tion (see Reagents) and let stand with occasional shaking for one- 
half hour. Add 10 ce of the 15 per cent potassium iodide solu- 
tion and 100 cc of water and titrate with standard sodium thio- 
sulphate, using starch as indicator. ‘The titrations on the two 
blank tests should agree within 0.1 cc. From the difference be- 
tween the average of the blank titrations and the titration on the 


Specification for Leaded Zinc Oxide, Dry and Paste y, 


sample. and the iodine value of the thiosulphate solution calculate 
the iodine number of the sample tested. (Iodine number is centi- 
grams of iodine to 1 g of sample.) If the iodine number is less 
than 170, the oil does not meet the specification. 

(1) COARSE PARTICLES AND ‘“‘SKINS.’’—Weigh an amount of 
paste containing 10 g of pigment (see 4(d)), add roo g of kerosene 
and wash through a No. 325 screen. The residue is reported as 
‘““coarse particles and ‘skins.’ ”’ 


5. REAGENTS. 


(a) URANYL INDICATOR FoR Zinc TITRATION.—A 5 per cent 
solution of uranyl nitrate in water or a 5 per cent solution of 
uranyl acetate in water made slightly acid with acetic acid. 

(b) STANDARD PoTasstuM FERROCYANIDE.—Dissolve 22 g of 
the pure salt in water and dilute to 1,000 cc. To standardize, 
transfer about 0.2 g (accurately weighed) of pure metallic zinc or 
freshly ignited pure zinc oxide to a 400 cc beaker. Dissolve in 
10 ec of hydrochloric acid and 20 cc of water. Drop in a small 
piece of litmus paper, add ammonium hydroxide until slightly 
alkaline, then’ add hydrochloric acid until just acid and then add 
3 ec of strong hydrochloric acid. Dilute to about 250 cc with 
hot water and heat nearly to boiling. Run in the ferrocyanide 
solution slowly from a burette with constant stirring until a drop 
tested on a white porcelain plate with a drop of the uranyl indi- 
cator shows a brown tinge after standing one minute. A blank 
should be run, using the same amounts of reagents and water as in 
the standardization. The amount of ferrocyanide solution re- 
quired for the blank should be subtracted from the amounts used 
in standardization and in titration of the sample. The standardi- 
zation must be made under the same conditions of temperature, 
volume, and acidity as obtain when the sample is titrated. 

(c) BartuM CHLORIDE SoLuTION.—Dissolve 100 g of pure 
crystallized barium chloride in water and dilute to 1,000 cc. 

(d) STANDARD SODIUM THIOSULPHATE SOLUTION.— Dissolve pure 
sodium thiosulphate in distilled water that has been well boiled 
to free it from carbon dioxide, in the proportion of 24.83 g of 
crystallized sodium thiosulphate to 1,000 cc of the solution. It 
is best to let this solution stand for about two weeks before stand- 
ardizing. Standardize with pure resublimed iodine (See Ana- 
lytical Chemistry, Treadwell-Hall, 2, 3d ed., p. 646). This solu- 
tion will be approximately decinormal, and it is best to leave it as 


8 Circular of the Bureau of Standards 


it is after determining its exact iodine value, rather than to 
attempt to adjust it to exactly decinormal. Preserve in a stock 
bottle provided with a guard tube filled with soda lime. 

(ec) STtaRCH SOLUTION.—Stir up 2 to 3 g of potato starch or 5 g 
of soluble starch with 100 cc of 1 per cent salicylic acid solution, 
add 300 to 400 cc of boiling water, and boil the mixture until the 
starch is practically dissolved, then dilute to 1 liter. 

(f) EXTRACTION MIXTURE.— 

10 volumes ether (ethyl ether). 
6 volumes benzol. 
4 volumes methyl alcohol. 
1 volume acetone. 

(g) AguEOUs SopiumM HyproxIbE.—Dissolve 100 g of sodium 
hydroxide in distilled water and dilute to 300 cc. 

(hk) Porasstum IopIDE SoLUTION.— Dissolve 150 g of senate 
iodide free from iodate, in distilled water and dilute to 1,000 cc 

(1) Hanus SOLUTION.—Dissolve 13.2 g of iodine in 1,000 ce of 
99.5 per cent glacial acetic acid, which will not reduce chromic 
acid. Add enough bromine to double the halogen content, deter- 
mined by titration (3 cc of bromine is-about the proper amount). 
The iodine may be dissolved by the aid of heat, but the solution 
should be cold when the bromine is added. 

(7) ALCOHOLIC SopIUM HypDROXIDE SOLUTION.—Dissolve pure 
sodium hydroxide in 95 per cent ethyl alcohol in the proportion 
of about 22 g per 1,000 cc. Let stand in a stoppered bottle. 
Decant the clear liquid into another bottle, and keep well stop- 
pered. This solution should be colorless or only slightly yellow 
when used, and it will keep colorless longer if the alcohol is pre- 
viously treated with sodium hydroxide (about 80 g to 1,000 cc), 
kept at about 50° C. for 15 days, and then distilled. 


ADDITIONAL COPIES 


OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 

AT 
5 CENTS PER COPY 


WASHINGTON : GOVERNMENT PRINTING OFFIC : 1924 


DEPARTMENT OF COMMERCE. 
Ant BUREAU OF STANDARDS. 


S. W. STRATTON, Director. 


CIRCULAR OF THE BUREAU OF STANDARDS. 
No. 89. 


{2d edition. Issued July 3, 1922.] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
WHITE PAINT AND TINTED PAINTS MADE ON A 
WHITE BASE, SEMIPASTE AND READY MIXED.’ 


Oe 


FEDERAL SPECIFICATIONS BOARD. 
STANDARD SPECIFICATION NO. 10. 


This Specification was officially adopted by the Federal Specifications Board on 
February 3, 1922, for the use of the Departments and Independent Establish- 
ments of the Government in the purchase of materials covered by it. 


CONTENTS. 


Page 
ee te Bi) omit bare cert ane (29 heir © or 
RM ERE SU. haley, IR (cle dew Ae eva «td Rae putilye ev oe aWidle 9 ag . 3 
9) LGboraveny GmamINALON oem paste... 2. ck ek eee pee cee ne renne« 3 
ee aie sere. SEI. SIRO. OR LAA, Ba CAB AEA, ot 6 
Ra hanoratory ecamination—Mixed paint... topes) 1s rept srca'y sald. oh Dyas 7 
Pe a eg RN i hn face 5 ob ie ain Be hk ty hs LEMAR no pele aa pekaed 4 8 


1. GENERAL. 


White paint and tinted paints made on a white base may be 
ordered either in the form of semipaste pigment ground in linseed 
oil or of ready-mixed paint. 

The semipaste shall be purchased by net weight, the ready-mixed 
paint either by weight or volume (231 cubic inches to the gallon). 

(a) PIGMENT.—The pigment shall be composed of: 


Maximum.| Minimum. 


Per cent. | Per cent. 
White lead (basic carbonate, basic sulphate, or a mixture thereof)................ 70 45 


Zanic Orde (ZNO)... ...). 5. ¢ ota» Domandd eaigawdgea sh aaah. pee Suaisbislent. sige 16S. Beh 55 30 
White mineral pigments, containing no lead or zinc compounds, pure tinting 
MOLE GY TUIXCUITC TMCLOO! 5 icin ser da.c sin vile ae a0 oie gna e 4.0 p inih exer Vintharein) Dy opicew eiphe 15 0 


1It is believed that this specification admits practically all high-grade prepared paints generally avail- 
ablein the United States, and which are therefore obtainable without requiring manufacturers to make 
up speciallots. On large contracts for which paint will be specially made, the purchaser may require 
the bidder to submit the formulaof the paint he proposes tofurnish as conforming to the specifications. 


109840°—22—.-1 


2 Circular of the Bureau of Standards 


In no case shall the sum of the basic lead carbonate, basic lead 
sulphate, and zinc oxide be less than 85 per cent. The lead and 
zinc pigments may be introduced in the form of any mixture 
preferred of basic carbonate white lead, basic sulphate white lead, 
zinc oxide, or leaded zinc, provided the above requirements as to 
composition are met. The total lead dissolved by dilute acetic 
acid and hot acid ammonium acetate, weighed as lead sulphate, 
and this weight multiplied by the factor 0.883 shall be considered 
white lead. (It is not possible to determine the amount of lead 
carbonate and lead sulphate when carbonates or sulphates of 
other metals such as calcium are present. Also neither basic lead 
carbonate nor basic lead sulphate are definite compounds. The 
factor to convert PbSO, to (PbCO,), Pb(OH), is 0.854, to convert 
PbSO, to PbSO,PbO is 0.868, and to convert PbSO, to (PbSO,), 
PbO is 0.913. The arbitrary factor used under this specification 
is the mean of the largest and smallest of these three factors. 

(6) Ligurp.—The liquid in semipaste paint shall be entirely 
pure raw or refined linseed oil; in ready-mixed paint it shall con- 
tain not less than go per cent pure raw linseed oil, the balance to 
be combined drier and thinner. The thinner shall be turpentine, 
volatile mineral spirits, or a mixture thereof. 

(c) SEMIPASTE.—Semipaste shall be made by thoroughly grind- 
ing the pigment with pure raw or refined linseed oil. 

The semipaste as received and three months thereafter shall be 
not caked in the container and shall break up readily in linseed 
oil to form a smooth paint of brushing consistency. It shall mix 
readily with linseed oil, turpentine, or volatile mineral spirits, or 
any combination of these substances, in all proportions without 
curdling. The color and hiding power when specified shall be 
equal to that of a sample mutually agreed upon by buyer and 
seller. The weight per gallon shall be not less than 19.0 pounds. 
The paste shall consist of: 


Maximum.) Minimum. 


Per cent. | Per cent. 
PUCMENE och, osccve.s a gaievidews ws cae + ete Nite ah el Oke 77 73 
LARSOOEPON 5 EY FOR LS so accu bars 5 gs data eM cinema G2 od a2 27 23 
Moisture and other volatile matter...... 40 8U02) Sorry. cl a ee at Pi ay Riel a Ph 
Coarse particles and ‘‘skins”’ (total residue retained on No. 325 screen based on 
pigment)... oo... ee cutee eek RL RR, Shee ee: 2) 0 ay ery beh cyt 


(dq) Reapy-MrxEp Parint.—Ready-mixed paints shall be well 
ground, shall not settle badly or cake in the container, shall be 
readily broken up with a paddle to a smooth uniform paint of good 


~ 


Specification for White Paint 3 


brushing consistency, and shall dry within 18 hours to a full oil 
gloss, without streaking, running, or sagging. The color and 
hiding power when specified shall be equal to those of a sample 
mutually agreed upon by buyer and seller. The weight per gallon 
shall be not less than 1534 pounds. The paint shall consist of: 


Maximum. | Minimum. 


Per cent. | Per cent. 
ee Pea ee MERA, GSE e 8s S8 559.5 dase tet att Sale SELLE <SREERAG LOE 66 62 
Liquid ( clans at least 90 per cent linseed oil).........0.... 0. ccc eee cece eee 38 34 
De ee ee Tc natn Ab wank + Acura ds gad ais ss. fd o-aey <giee ek Lee oS OD ses lappa gees 
Coarse taggers and ‘‘skins’’ (total residue retained on No. 325 screen based on 
a aa. sacred us os tao ges Gre Emma emt «cb eos Ane oecmene VAN Sta Pe eres 


NorTe.— Deliveries will, in general, be sampled and tested by the following methods, but the purchaser 
reserves the right to use any additional available information to ascertain whether the ‘material meets the 


specification - 
2. SAMPLING. 


It is mutually agreed by buyer and seller that a single package 
out of each lot of not more than 1,000 packages shall be taken as 
representative of the whole. Whenever possible an original un- 
opened container shall be sent to the laboratory, and when this is 
for any reason not done, the inspector shall determine by thorough 
testing with a paddle or spatula whether the material meets the 
requirement regarding caking in the container. He shall then 
thoroughly mix the contents of the container and draw a sample 
of not less than 5 pounds of the thoroughly mixed paint, place it in 
a clean, dry metal or glass container, which must be filled with the 
sample, closed with a tight cover, sealed, marked, and sent to the 
laboratory for test with the inspector’s report on caking in con- 
tainer. 

When requested, a duplicate sample may be taken from the same 
package and delivered to the seller, and the inspector may take a 
third sample to hold for test in case of dispute. 


3. LABORATORY EXAMINATION—SEMIPASTE. 


(a) CAKING IN CONTAINER.—When an original package is re- 
ceived in the laboratory it shall be weighed, opened, and stirred 
with a stiff spatula or paddle. The paste must be no more diffi- 
cult to break up than a normal good grade of semipaste paint. 
The semipaste shall finally be thoroughly mixed, removed from 
the container, and the container wiped clean and weighed. This 
weight subtracted from the weight of the original package gives 
the net weight of the contents. A portion of thoroughly mixed 


4 Circular of the Bureau of Standards 


semipaste shall be placed in a clean container and the portions for 
the remaining tests promptly weighed out. 

(b) CoLorR.—Place some of the paint on a clean, clear glass plate. 
Place some of the standard agreed upon beside the sample on the 
plate, turn the glass over, and compare the colors. 

(c) WEIGHT PER GALLON.—From the weight of a known volume 
of the paste calculate the specific gravity, which multiplied by 
8.33 gives the weight in pounds per gallon. Any suitable con- 
tainer of known volume may be used for the purpose, but a short 
cylinder of heavy glass with rounded bottom about 75 mm high 
and having a capacity of from 125 to 175 cc (a glass cap to keep 
dust from reagent bottle stopper) is a convenient apparatus for 
the purpose. The capacity of this vessel is determined to within 
1 cc. The paste is packed into it until completely full, the top 
leveled off smooth with a spatula, and weighed to +0.5 g. Sub- 
tract the weight of the empty container and divide the remainder 
by the number of cubic centimeters representing the capacity of 
the container. The quotient is the specific gravity, which can be 
thus determined within +2 in the second decimal place. 

(2) MrxInc wirH LINSEED O1L.—One hundred grams of the 
paste shall be placed in a cup, 18 cc linseed oil added slowly with 
careful stirring and mixing with a spatula or paddle. The result- 
ing mixture must be smooth and of good brushing consistency. 

(e) MOISTURE AND OTHER VOLATILE MATTER.—Weigh accu- 
rately from 3 to 5 g of the paste into a tared flat-bottomed dish 
about 5 cm in diameter, spreading the paste over the bottom. 
Heat at 105 to 110° C. for one hour, cool, and weigh. Calculate 
loss in weight as percentage of moisture and volatile matter. 

({) PERCENTAGE OF PIGMENT.—Weigh accurately about 15 g of 
the paste into a weighed centrifuge tube. Add 20 to 30 cc of 
“extraction mixture” (see reagents), mix thoroughly with a glass 
rod, wash the rod with more of the extraction mixture, and add 
sufficient of the reagent to make a total of 60 cc in the tube. 
Place the tube in the container of a centrifuge, surround with 
water, and counterbalance the container of the opposite arm 
with a similar tube or a tube with water. ‘ Whirl at a moderate 
speed until well settled. Decant’ the clear supernatant liquid. 
Repeat the extraction twice with 40 cc of extraction mixture and 
once with 4o cc of ether. After drawing off the ether, set the 
tube in a beaker of water at about 80° C. or on top of a warm oven ~ 
for Io minutes, then in an oven at 110 to 115° C. for two hours. » 


Specification for White Paint 5 


Cool, weigh, and calculate the percentage of pigment. Grind 
the pigment to a fine powder, pass through a No. 80 screen to re- 
move any skins, and preserve in a stoppered bottle. 

(g) PREPARATION OF Farry Acips.—To about 25 g of the paste 
in a porcelain casserole, add 15 cc of aqueous sodium hydroxide 
(see reagents) and 75 cc of ethyl alcohol mix and heat uncovered 
on a steam bath until saponification is complete (about one hour). 
Add 100 ec of water, boil, add an excess of sulphuric acid of 
specific gravity 1.2 (8 to 10 cc will usually suffice), boil, stir, and 
transfer to a separatory funnel to which some water has been 
previously added. Draw off as much as possible of the acid 
aqueous layer and lead sulphate precipitate, wash once with 
water, then add 50 cc of water and 50 cc of ether. Shake very 
gently with a whirling motion to dissolve the fatty acids in the 
ether, but not so violently as to form an emulsion. Draw off 
the aqueous layer and wash the ether layer with one 15 cc portion 
of water and then with 5 cc portions of water until free from 
sulphuric acid. Then draw off the water layer completely. 
Transfer the ether solution to a dry flask and add 25 to 50 g 
anhydrous sodium sulphate. Stopper the flask and let stand 
with occasional shaking at a temperature below 25° C. until the 
water is completely removed from the ether solution, which will 
be shown by the solution becoming perfectly clear above the 
solid sodium sulphate. Decant this clear solution, if necessary 
through a dry filter paper, into a dry too cc Erlenmeyer flask. 
Pass a rapid current of dry air (pass through a CaCl, tower) into 
the mouth of the Erlenmeyer flask and heat to a temperature 
below 75° C. on a dry hot plate until the ether is entirely driven off. 

NoTEe.—It is important to follow all of the details, since ether generally contains 
alcohol and after washing with water always contains water. It is very difficult 
to remove water and alcohol by evaporation from fatty acids, but the washing of the 
ether solution and subsequent drying with anhydrous sodium sulphate removes both 
water and alcohol. Ether, in the absence of water and alcohol, is easily removed 
from fatty acids by gentle heat. 

The fatty acids prepared as above should be kept in a stoppered 
flask and examined at once. 

(h) TEST FOR MINERAL OIL AND OTHER UNSAPONIFIABLE 
MatTTrEerR.—Place 10 drops of the fatty acid (g) in a 50 cc test 
tube, add 5 ce of alcoholic soda (see reagents), boil vigorously 
for five minutes, add 40 cc of water, and mix; a clear solution 
indicates that not more than traces of unsapontfiable matter are 
present. If the solution is not clear, the oil is not pure linseed oil. 


109840°—22 2 


6 Circular of the Bureau of Standards 


(t) IopINE NUMBER oF Farry Acips.—Place a small quantity 
of the fatty acids (g) in a small weighing burette or beaker. Weigh 
accurately. Transfer by dropping about 0.15 g (0.10 to 0.20 g) 
into a 500 cc bottle having a well-ground glass stopper, or an 
Erlenmeyer flask having a specially flanged neck for the iodine 
test. Reweigh the burette or beaker and determine amount of 
sample used. Addt1occ of chloroform. Whirl the bottle to dis- 
solve the sample. Add 1occ of chloroform to two empty bottles 
like that used for the sample. Add to each bottle 25 cc of the 
Hanus solution (see reagents) and let stand with occasional 
shaking for one-half hour. Add t1occ of the 15 per cent potassium 
iodide solution and 100 cc of water, and titrate with standard 
sodium thiosulphate using starch as indicator. ‘The titrations 
on the two blank tests should agree within 0.1 cc. From the 
difference between the average of the blank titrations and the 
titration on the sample and the iodine value of the thiosulphate 
solution, calculate the iodine number of the sample tested. (Iodine 
number is centigrams of iodine to 1 g of sample.) If the iodine 
number is less than 170, the oil does not meet the specification. 

(j) COARSE PaRTICLES AND SKINS.—Dry in an oven at 105 to 
110° C. a No. 325 screen, cool, and weigh accurately. Weigh an 
amount of semipaste containing 10 g of pigment (see 3 (f)), add 
100 cc of kerosene, mix thoroughly, and wash with kerosene 
through the screen, breaking up all lumps, but not grinding. After 
washing with kerosene until all but the particles too coarse to pass 
the screen have been washed through, wash all kerosene from the 
screen with ether or petroleum ether, heat the screen for one hour 
at 105 to 110° C., cool, and weigh. 


4, ANALYSIS OF PIGMENT. 


(a) QUALITATIVE ANALYsIs.—A complete qualitative analysis 
following the well-established methods is always advisable, but the 
work may be usually very much shortened by adding acetic acid 
slowly to the pigment until all carbonate is decomposed (noting 
whether any hydrogen sulphide is evolved), then adding a large © 
excess of acid ammonium acetate, boiling, filtering, and testing 
the filtrate for metals other than lead and zinc (especially calcium 
and barium). The absence of calcium in this filtrate indicates 
that the extending pigments contain no calcium carbonate or 
calcium sulphate; the absence of barium indicates that the extend- 
ing pigments contain no barium carbonate. ‘Test another portion 


Specification for White Paint 7 


of pigment with hydrochloric acid (1:1). No odor of hydrogen 
sulphide should develop. 

(0) Wurre Leap.—Weigh accurately about 1 g of the pigment, 
transfer to a 250 cc beaker, moisten with a few drops of alcohol, 
add slowly dilute (about 20 per cent) acetic acid until all car-- 
bonate is decomposed (no further effervescence), then add 50 cc 
of acid ammonium acetate solution (see reagents), and boil for 
two minutes. Decant through a weighed Gooch crucible, leaving 
any undecomposed matter in the beaker. Wash the Gooch 
crucible with a small amount (about 20 cc) of hot water. ‘Tio the 
residue in the beaker add 50 cc of the acid ammonium acetate 
solution and boil two minutes. Filter through the same Gooch 
crucible, transferring the insoluble matter to the crucible, and 
wash thoroughly with hot water. Dry the crucible at 105 to 120° 
C., cool, and weigh. In cases where siliceous material was used 
as the white extending pigments, the material retained on the 
Gooch crucible will approximate the amount of white extending 
and tinting pigments. 

Unite the filtrates and pass in a stream of hydrogen sulphide 
to complete precipitation; let the mixed sulphides of lead and 
zinc settle, filter on paper, wash with water containing hydrogen 
sulphide, dissolve the sulphides in hot nitric acid (1:3), and deter- 
mine lead as sulphate in the usual manner, weighing as PbSO,,. 
Multiply lead sulphate weight by the factor 0.883 and report as 
white lead. 

(c) ZINC OxmpE.—Weigh accurately about 1 g of the pigment, 
transfer to a 400 cc beaker, ‘add 30 cc of hydrochloric acid (1:2), 
boil for two or three minutes, add 200 cc of water and a small 
piece of litmus paper; add strong ammonia until slightly alkaline, 
render just acid with hydrochloric acid, then add 3 cc of strong 
hydrochloric acid, heat nearly to boiling, and titrate with standard 
ferrocyanide as in standardizing that solution (see reagents). 
Calculate total zinc as zinc oxide. 

(d) Calculations ——Add the percentage of white lead (see 4(0)), 
zinc oxide (see 4(c)), and subtract from 100; the remainder is 
reported as extending and tinting pigments. 


5. LABORATORY EXAMINATION—MIXED PAINT. 


(a) CAKING IN CONTAINER.—Follow the procedure outlined in 
3(a), noting that the paint should be no more difficult to break 
up than a good grade of mixed paint. 


8 Circular of the Bureau of Standards 


(b) CoLor.—Follow the procedure outlined in 3(6). 

(c) WEIGHT PER GALLON.—Weigh a clean, dry, 100 ce grad- 
‘uated flask. Fill to the mark with the thoroughly mixed paint 
and weigh again. The increase in weight expressed in grams, 
divided by 100, gives the specific gravity, which multiplied by 
8.33 gives the weight in pounds per gallon. 

(d) BRUSHING PROPERTIES AND Time oF Dryinc.—Brush the 
well-mixed paint on a suitable panel, which may be ground glass, 
steel, or well-filled wood. Note whether the paint works satis- 
factorily under the brush. Place the panel in a vertical position 
in a well-ventilated room and let stand for 18 hours. The paint 
should be dry and free from streaks. 

(ce) WaTER.—Mix 100g of the paint in a 300 cc flask with 75 
ec of toluol. Connect with a condenser and distill until about 
50cc of distillate has been collected in a graduate. The tempera- 
ture in the flask should be then about 105 to 110° C. The num- 
ber of cubic centimeters of water collecting under the toluol in 
the receiver is the percentage of water in the paint. 

(f) VOLATILE THINNER.—Follow the procedure outlined in 
3(e). Correct the result for any water found (see 5(e)) and report 
the remainder as volatile thinner. 

(g) PERCENTAGE OF PIGMENT.—Follow the procedure outlined 
in 3(/). 

(hk) TestiInG NONVOLATILE VEHICLE.—Follow the procedure 
outlined in 3(g), 3(h), and 3(z), except that in the preparation of 
the fatty acids the mixture of paint and alkali is heated on the 
steam bath until all volatile thinner is driven off. 

(t) CoARSE PARTICLES AND SKINS.—Follow the procedure out- 
lined in 3(9). 

(j) TESTING PIGMENT.—Follow the Process outlined in 4(a) 
to 4(d), inclusive. 

6. REAGENTS. 


(a) Actp AMMONIUM ACETATE SOLUTION.—Mix 150 ce of 80 
per cent acetic acid, 100 cc of water, and 95 cc of strong am- 
monia (specific gravity, 0.90). 

(b) URANYL INDICATOR FOR ZINC TYTRATION. —A 5 per cent 
solution of uranyl nitrate in water or a 5 per cent solution of 
uranyl acetate in water made slightly acid with acetic acid. 

(c) StanparD PorasstuM FERROCYANIDE.—Dissolve 22 g of 
the pure salt in water and dilute to 1,000 ce. To standardize, 


Specification for White Paint 9 


transfer about 0.2 g (accurately weighed) of pure metallic zine or 
freshly ignited pure zinc oxide to a 400 cc beaker. Dissolve in 
10 cc of hydrochloric acid and 20 ce of water. Drop in a small 
piece of litmus paper, add ammonium hydroxide until slightly 
alkaline, then add hydrochloric acid until just acid, and then Pee & 
of strong hydrochloric acid. Dilute to about 250 ce with hot 
water and heat‘nearly to boiling. Run in the ferrocyanide solu- 
tion slowly from a burette with constant stirring until a drop 
tested on a white porcelain plate with a drop of the uranyl indi- 
cator shows a brown tinge after standing one minute. A blank 
should be run with the same amounts of reagents and water as in 
the standardization. The amount of ferrocyanide solution re- 
quired for the blank should be subtracted from the amounts used 
in standardization and in titration of the sample. ‘The standardi- 
zation must be made under the same conditions of temperature, 
volume, and acidity as obtained when the sample is titrated. 

(d) STANDARD SODIUM THIOSULPHATE SOLUTION.— Dissolve pure 
sodium thiosulphate in distilled water (that has been well boiled 
to free it from carbon dioxide) in the proportion of 24.83 g crystal- 
lized sodium thiosulphate te 1,000 cc of the solution. It is 
best to let this solution stand for about two weeks before stand- 
ardizing. Standardize with pure resublimed iodine. (See Tread- 
well-Hall, Analytical Chemistry, vol. 2, 3d ed., p. 646,)° {iis 
solution will be approximately decinormal, and it is best to leave 
it as it is after determining its exact iodine value, rather than to 
attempt to adjust it to exactly decinormal. Preserve in a stock 
bottle provided with a guard tube filled with soda lime. 

(e) STARCH SOLUTION.—Stir up 2 to 3 g of potato starch or 
5 g of soluble starch with 100 cc of 1 per cent salicylic acid solu- 
tion, add 300 to 400 cc boiling water, and boil the mixture until 
the starch is practically dissolved, then dilute to 1 liter. 

(f) EXTRACTION MIxTURE.— 

10 volumes ether (ethyl ether). 
6 volumes benzol. 
4 volumes methyl alcohol. 
I volume acetone. 

(g) AguEous Soprum HyproxipE.—Dissolve 100 g of sodium 
hydroxide in distilled water and dilute to 300 cc. 

(h) Porasstum IopipE SoLuTION.—Dissolve 150 g of potassium 
iodide free from iodate in distilled water and dilute to 1,000 cc 


IO Circular of the Bureau of Standards 


(i) Hanus SoLuTION.—Dissolve 13.2 g of iodine in 1,000 ce of 
99.5 per cent glacial acetic acid, which will not reduce chromic 
acid. Add enough bromine to double the halogen content, 
determined by titration (3 cc of bromine is about the proper 
amount). The iodine may be dissolved by the aid of heat, but 
the solution should be cold when the bromine is added. 

(j) ALCoHOLIc Soprum HypRoxIDE SoL_uTION.—Dissolve pure 
sodium hydroxide in 95 per cent ethyl alcohol in the proportion 
of about 22 g per 1,000cc. Let stand in a stoppered bottle. 
Decant the clear liquid into another bottle and keep well stoppered. 
This solution should be colorless or only slightly yellow when used, 
and it will keep colorless longer if the alcohol is previously treated 
with sodium hydroxide (about 80 g to 1,000 cc), kept at about 
50° C. for 15 days, and then distilled. 


ADDITIONAL COPIES 


OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 

AT 


5 CENTS PER COPY 
V 


DEPARTMENT OF COMMERCE 
BUREAU OF STANDARDS 3 


S. W. STRATTON, Director 


CIRCULAR OF THE BUREAU OF STANDARDS 
No. 90 


(2d edition. Issued May 23, 1922] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
RED LEAD—DRY AND PASTE 


ee eet 


FEDERAL SPECIFICATIONS BOARD 
STANDARD SPECIFICATION NO. 11 


This Specification was officially adopted by the Federal Specifications Board, 
on February 3, 1922, for the use of the Departments and Independent Establish- 
ments of the Government in the purchase of materials covered by it. 


CONTENTS 

Page 
a cae wes ay cat gin Bho sMh oguh de aig 4. ES cdahice a shalt I 
ARE Re a Se Se ieee ci hays Cos bain sua cen nde eee 3 
3- Laboratory examination, dry pigment................. FRE RMN RE 3 
eee eo eiineuon, paste eri wis en ee eS 5 
ee hie hc vow cies ooh tad helies oo eee x 

1. GENERAL 


Red lead may be ordered in the form of dry pigment or of 
paste ground in pure raw linseed oil. Two grades of pigment, 
known as 85 and 95 per cent, may be ordered, and each contract 
shall state which grade is desired.' 

Material shall be bought by net weight. 

1 Avoid storing red-lead paste in places of high temperature, as heat accelerates the tendency of this 
material to cake or harden. Purchasers are cautioned not to buy red lead in paste form unless it is to be 


used within three months after shipment by the contractor. 
63910°—23 


2 Circular of the Bureau of Standards 


(a) Dry Picment.—The pigment shall consist entirely of oxides 
of lead free from all adulterants and shall meet the following 
requirements: 


85 per cent | 95 per cent 
grade . grade 


anna nna 


* Per cent Per cent 
True red lead (Pb,O,), not less than......-.--------------- 25 95 
Total impurities, including moisture, soluble matter, water— 

and matter insoluble in a mixture of nitric acid and 

hydrogen peroxide, not more than.....-------------+-+--:- 1 1 
Remainder shall be lead monoxide (PbO). 
Coarse particles: Retained on standard No. 325 screen, not 

more than. ......-i2-2<.-«¢9Uls 80 Salt ener - eee | 2.0 1.0 


When mixed with raw linseed oil, turpentine, and liquid drier 
in the proportions 


Dry red lead... 000.2... 65s ele See 3 4a 2 ene ae pounds.. 20 
Raw linseed oil. 2... esa eee 2 eee 2 pints... § 
Turpentine {6 002d. Se ec) 5 Pte Sates es een ie Rs gills... <2 
Liquid drier... 2... nue evens eae cage as se Reis dO. <aenge 


the resulting paint when brushed on a smooth vertical iron surface 
shall dry hard and elastic without running, streaking, or sagging. 

(b) Paste.—The paste shall be made by thoroughly grinding the 
specified grade of dry pigment with pure raw or refined linseed oil. 

The paste, as shipped by the contractor, and for three months 
thereafter, shall not be caked in the container and shall readily 
break up in oil to form a smooth paint of brushing consistency. 
‘The paste shall have the following composition: | 


ann anne Ven nse nnn en cence een ey STS 


Maximum Minimum 


Per cent Per cent 


Pigment. ....-.5...---2-+-ges++ == 2B Asgiee Ate b+ gs soe eee 94 92 
Linseed. oil. . 0c2 sveck6a ait cela oe ine 9 8 6 
Moisture and other volatile matter. .......----..----------- 0. Bikau. d20e0- +s 
Coarse particles and skins (total residue left on No. 325 

SCLEEN)... 2. cee ese he eee eee tne tee ceeded eee es 1.-Sr ls os yeaa ee 


ana nance coe nee ee PSS 


When mixed with raw linseed oil, turpentine, and liquid drier 
in the proportions 


Red lead pastes «:..50.552 sim vee Neila are 62 pounds.. 20 
Raw linseed oil. p00. 0c...) Se ee pints.. 4% 
Turpentine. 052) bk. 2s daw ewe we 8 Se gills. °°" 


Taquid drier... 0s .cies ee coe nuhnenaes 0s ces thn 28 7 ee COis.c5. 


Red Lead, Dry and Paste 3 


the resulting paint when brushed on a smooth vertical iron surface 
shall dry hard and elastic without running, streaking, or sagging. 


2. SAMPLING 


It is mutually agreed by buyer and seller that a single package . 
out of each lot of not more than 1000 packages be taken as repre- 
sentative of the whole. | 

With the dry pigment, this package is to be opened by the 
inspector and a sample of not less than 5 pounds taken at random 
from the contents and sent to the laboratory for test. When 
requested, a duplicate sample may be taken from the same package 
and delivered to the seller, and the inspector may take a third 
sample to hold for test in case of dispute. 

With the paste, whenever possible, an original unopened con- 
tainer shall be sent to the laboratory, and when this is for any 
reason not done, the inspectot shall determine by thoroughly 
testing with a paddle or spatula whether the material meets the 
requirement regarding not caking in the container (see 4 (a)). 
After assuring himself that the paste is not caked in the can, the 
inspector shall draw a sample of not less than 5 pounds of the 
thoroughly mixed. paste, place it in a clean dry metal or glass 
container, which must be filled with the sample, closed with a 
tight cover, sealed, marked, and sent to the laboratory for test 
with the inspector’s report on caking in container. 

Samples will, in general, be tested by the following methods, 
but the purchaser reserves the right to apply any additional 
tests, or use any available information to ascertain whether the 
material meets the specification. 


3. LABORATORY EXAMINATION, DRY PIGMENT 


(a) QUALITATIVE ANALysIs.—Follow ordinary methods of 
qualitative analysis. The material should give a negative test 
for matter insoluble in a mixture of nitric acid and hydrogen 
peroxide, and material other than oxides of lead. (If more thana 
faint cloud remains after treatment with nitric acid and hydrogen 
peroxide, it will be necessary to take a weighed sample and deter- 
mine the percentage of this insoluble matter.) Boil 2 g of the 
sample with 25 cc of 95 per cent ethyl alcohol, let settle, decant off 
the supernatant liquid, boil the residue with water, decant as 
before, and boil the residue with very dilute ammonia. If the 


4 * Circular of the Bureau of Standards 


alcohol, water, or ammonia are colored, organic coloring matter is 
indicated, which is cause for rejection. 

(b) TRuE RED LeAD.—Weigh accurately 1 g of the sample into 
a 200 cc Erlenmeyer flask, add a few drops of distilled water, and 
rub the mixture to a smooth paste with a glass rod flattened on 
the end. Mix in a small beaker 30 g of pure crystallized sodium 
acetate, 2.4 g of pure potassium iodide, 10 cc of water, and 10 cc 
of 50 per cent acetic acid. Stir until all is liquid, warm gently, 
and, if necessary, add 2 to 3 cc more water. Cool to room tem- 
perature and pour into’the flask containing the red lead. Rub 
with the glass rod until nearly all the red lead has been dissolved, 
add 30 cc of water containing 5 to 6 g of sodium acetate, and 
titrate at once with standard sodium thiosulphate solution, 
adding the latter rather slowly and keeping the liquid constantly 
in motion by whirling the flask. When the solution has become 
light yellow, rub any undissolved particles up with the rod until 
free iodine no longer forms, wash off the rod, and add the sodium 
thiosulphate solution until pale yellow. Add starch solution 
and titrate until colorless, add standard iodine solution until the 
blue color is just restored. From the amount of standard iodine 
solution used, calculate the correction to be applied to the thio- 
sulphate reading, and calculate true red lead (iodine value of 
thiosulphate x 2.7 = Pb,O, value). 

(c) WATER SOLUBLE MaTTreR.—Digest 10 g of the sample with 
200 cc of hot water on a steam bath for 1 hour; filter and wash 
with hot water until no residue is left on evaporating a few drops 
of the washings. Evaporate the filtrate to dryness in a weighed 
dish on a steam bath, heat for 30 minutes at 105 to 110° C, cool, 
and weigh. 

(d) COARSE PaRTICLES.—Dry in an oven at 105 to 110° Ca 
325 screen, cool, and weigh accurately. Weigh 25 g of the sample, . 
dry at 100° C, transfer to a mortar, add 100 cc kerosene, thor- 
oughly mix by gentle pressure with a pestle to break up all lumps, 
wash with kerosene through the screen, breaking up all lumps, but 
not grinding. After washing with kerosene until all but the parti- 
cles which are too coarse to pass the screen have been washed 
through, wash all kerosene from the screen with ether or petro- 
leum ether, heat the screen for one hour at 105 to 110° _ cool, 
and weigh.’ 


For a general discussion of screen tests of pigments and data regarding many pigments on the market, 
see Circular No. 148 of the Educational Bureau, Scientific Section, Paint Manufacturers’ Association of the 
United States. 


Red Lead, Dry and Paste 5 


(e) RUNNING, STREAKING, OR SAGGING.—Mix paint and apply 
as per specifications. About the smallest amount that can be 
conveniently made up will be 154 g dry red lead, 40 cc raw lin- 
seed oil, and 4 cc each of turpentine and liquid drier. 


4. LABORATORY EXAMINATION, PASTE 


(a) CakING In ConTaINER.—When an original package is re- 
ceived in the laboratory, it shall be weighed, opened, and stirred 
with a stiff spatula or paddle. The paste must be no more diffi- 
cult to break up and show no more caking than a normal good 
grade of red-lead paste. The paste shall finally be thoroughly 
mixed, removed from the container, the container wiped clean, 
and weighed. This weight subtracted from the weight of the 
original package gives the net weight of the contents. A portion 
of the thoroughly mixed paste shall be placed in a clean con- 
tainer and the portions for the remaining tests promptly weighed 
out. 

(6) MIxING witH LINSEED O1L, RUNNING, STREAKING, AND SAG- 
GING.—Mix as per specification to a paint, first using only the 
linseed oil and noting whether the paste breaks up readily and 
the resulting mixture issmooth. About the smallest amount that 
can be conveniently made up will be 154 g red-lead paste, 36 cc 
raw linseed oil, and 4 cc each of turpentine and liquid drier. 

(c) MOISTURE AND OTHER VOLATILE MarTrer.—Weigh accu- 
rately from 3 to 5 g of the paste into a tared flat-bottomed dish, 
about 5 cm in diameter, spreading the paste over the bottom. 
Heat at 105 to 110° C for one hour, cool, and weigh. Calculate 
the loss in weight as percentage of moisture and other volatile 
matter. 

(qd) PERCENTAGE OF PIGMENT.—Weigh accurately about 15 g 
of the paste into a weighed centrifuge tube. Add 20 to 30 cc 
of “‘extraction mixture’’ (see reagents), mix thoroughly with a 
glass rod, wash the rod with more of the extraction mixture, and 
add sufficient of the reagent to make a total of 60 cc in the tube. 
Place the tube in the container of a centrifuge, surround with 
water, and counterbalance the container of the opposite arm with 
a similar tube or a tube with water. Whirl at a moderate speed 
untilclear. Decant the clear supernatant liquid. Repeat the ex- 
traction twice with 4o cc of extraction mixture, and once with 40 
cc of ether. After drawing off the ether, set the tube in a beaker 
of water at about 80° C or on top of a warm oven for 10 minutes, 


6 | Circular of the Bureau of Standards 


then in an oven at 110 to 115° C for 2 hours. Cool, weigh, and 
calculate percentage of pigment. 

(ce) EXAMINATION OF PicMENT.—Grind the pigment from (d) 
to a fine powder, pass through a No. 80 screen to remove any 
“skins,” preserve in a stoppered tube, and apply tests 3 (a), 
3 (0), and 3 (c). 

(f) PREPARATION OF Farry Acips.—To about 25 g of the paste 
in a porcelain casserole, add 15 ec of aqueous sodium hydroxide 
(see reagents), and 75 cc of ethyl alcohol, mix and heat uncov- 
ered on a steam bath until saponification is complete (about one 
_hour). Add roo ce of water, boil, add sulphuric acid of specific 
gravity 1.2 (8 to 10 cc in excess), boil, stir, and transfer to a 
separatory funnel to which some water has been previously 
added. Draw off as much as possible of the acid aqueous layer 
and lead sulphate precipitate, wash once with water; then add 
50 cc water and 50 cc ether. Shake very gently with a whirling 
motion to dissolve the fatty acids in the ether, but not violently, 
so as to avoid forming an emulsion. Draw off the aqueous layer 
and wash the ether layer with one 15 ce portion of water and then 
with 5 cc portions of water until free from sulphuric acid. Then 
draw off the water layer completely. Transfer the ether solution 
to a dry flask, add 25 to 50 g of anhydrous sodium sulphate. 
Stopper the flask and let stand with occasional shaking at a tem- 
perature below 25° C until the water is completely removed from 
the ether solution, which will be shown by the solution becoming 
perfectly clear above the solid sodium sulphate. Decant this clear 
solution (if necessary through a dry filter paper) into a dry 100 cc 
Erlenmeyer flask. Pass a rapid current of dry air (Pass through 
CaCl, tower) into the mouth of the Erlenmeyer flask and heat to 
a temperature below 75° C on a dry hot plate until the ether is 
entirely driven off. The fatty acids prepared as above should be 
kept in a stoppered flask and examined at once. 

Nots.—It is important to follow all of the details, since ether generally contains 
alcohol, and after washing with water always contains water. It is very difficult to 
remove water and alcohol by evaporation from fatty acids, but the washing of the 
ether solution and subsequent drying with anhydrous sodium sulphate removes 
both water and alcohol. Ether, in the absence of water and alcohol, is easily removed 
from fatty acids by gentle heat. . 

(g) TEST FOR MINERAL O1L.—Place 10 drops of the fatty acid (/) 
in a 50 cc test tube, add 5 cc of alcoholic soda (see reagents), boil 
vigorously for five minutes, add 40 cc of water, and mix; a clear 
solution indicates that not more than traces of unsaponifiable 


Bt 


EE I ee ee ae ne ee 


Red Lead, Dry and Paste 7 


matter are present. If the solution is not clear, the oil is not pure 
linseed oil. 

(1) loprnE Number oF Farry Acips.—Place a small quantity 
of the fatty acids (f) in a small weighing burette or beaker. Weigh 
accurately. ‘Transfer by dropping about 0.15 g (0.10 to 0.20 g) to. 
a 500 cc bottle having a well-ground glass-stopper, or an Erlen- 
meyer flask having a specially flanged neck for the iodine test. 
Reweigh the burette or beaker and determine the amount of sam- 
ple used. Add tocc of chloroform. Whirl the bottle to dissolve 
the sample. Add 10 cc of chloroform to two empty bottles like 
that used for sample. Add to each bottle 25 cc of the Hanus 
solution (see reagents) and let stand with occasional shaking for 
one-half hour. Add to cc of the 15 per cent potassium iodide 
solution and 100 cc of water, and titrate with standard sodium 
thiosulphate, using starch asindicator. The titrations on the two 
blank tests should agree within 0.1 cc. From the difference be- 
tween the average of the blank titrations and the titration on the 
sample and the iodine value of the thiosulphate solution, calculate 
the iodine number of the sample tested. (Iodine number is centi- 
grams of iodine to 1 g of sample.) If the iodine number is less 
than 170, the oil does not meet the specification. 

(2) COARSE PARTICLES AND SKINS.—Weigh an amount of paste 
containing 25 g of pigment (see 4 (d)), add 200 cc of kerosene, and 
wash through a No. 325 screen as in 3 (d). 


5. REAGENTS 


(a) EXTRACTION MiIxtTuRE.— 
10 volumes ether (ethyl ether). 
6 volumes benzol. 
4 volumes methyl alcohol. 
I volume acetone. 

(6) AguEOUuS Sopium HyproxipE.—Dissolve 100 g of sodium 
hydroxide in distilled water and dilute to 300 cc. 

(c) STANDARD SopIUM ‘THIOSULPHATE SOLUTION.—Dissolve 
pure sodium thiosulphate in distilled water that has been well 
boiled to free it from carbon dioxide, in the proportion of 24.83 g 
of crystallized sodium thiosulphate to 1000 cc of the solution. It 
is best to let this solution stand for about two weeks before 
standardizing. Standardize with pure resublimed iodine. (See 
Treadwell-Hall, Analytical Chemistry, vol. 2, 3d ed., p. 646.) 
This solution will be approximately decinormal and it is best to 


8 Circular of the Bureau of Standards 


leave it as it is after determining its exact iodine value, rather than 
to attempt to adjust it to exactly decinormal. Preserve in a stock 
bottle provided with a guard tube filled with solda Jime. 

(d) Starcn SOLUTION.—Stir up 2 to 3 g of potato starch or 5 g 
of soluble starch with 100 ce of 1 per cent salicylic acid solution, 
add 300 to 400 cc of boiling water, and boil the mixture until the 
starch is practically dissolved, then dilute to 1 liter. 

(ec) StanDARD IODINE SOLUTION.—Dissolve 13 g of resublimed 
iodine and 18 g of pure potassium iodide (free from iodates) in 50 
ce of distilled water, and dilute to 1000 cc. Determine its exact 
value by titrating with the standard sodium thiosulphate solution. 

(f) Porasstum IoprpE SoLuTION.—Dissolve 150 g of potassium 
iodide, free from iodate, in distilled water and dilute to 1000 cc. 

(g) Hanus SoLuTION.—Dissolve 13.2 g of iodine in 1000 cc of 
99.5 per cent glacial acetic acid, which will not reduce chromic 
acid. Add enough bromine to double the halogen content, deter- 
mined by titration (3 cc of bromine is about the proper amount). 
The iodine may be dissolved by the aid of heat, but the solution 
should be cold when the bromine is added. 

(h) ALCoHOLIc Soprum HyproxIDE SoLUTION.—Dissolve pure 
sodium hydroxide in 95 per cent ethyl alcohol in the proportion 
of about 22 g per 1000 cc. Let stand in a stoppered bottle. De- 
cant the clear liquid into another bottle and keep well stoppered. 
This solution should be colorless or only slightly yellow when 
used, and it will keep colorless longer if the alcohol is previously 
treated with sodium hydroxide (about 80 g to 1000 cc), kept at 
about 50° C for 15 days, and then distilled. 


ADDITIONAL COPIES 


OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 

AT 


5CENTS PER COPY 
V 


DEPARTMENT OF COMMERCE 


BUREAU OF STANDARDS 
S. W. STRATTON, Director 


CIRCULAR OF THE BUREAU OF STANDARDS 
No. 91 


[2d edition, issued June 21, 1922] 
UNITED STATES GOVERNMENT SPECIFICATION FOR 
OCHER, DRY AND PASTE 


FEDERAL SPECIFICATIONS BOARD 
STANDARD SPECIFICATION NO. 12 


This Specification was officially adopted by the Federal Specifications Board 
on February 3, 1922, for the use of the Departments and Independent Establish- 
ments of the Government in the purchase of materials covered by it. 


CONTENTS 

Page 
ee Eee tte, fetta. si tsc: 2 oy Sets Gk. 1d. 2s, hie ce) LB I 
Be re oy ee py 2 
3. Laboratory examination of dry pigment. -....00. 2.2005... c cece kee eek 2 
a+) a0eratory examination of paste... v2. ee 4 
ee teks o8 gh. Saks | chp ce ets) ois Aven mcaricecabine. €arcagtiaee 7 

1. GENERAL 


Ocher may be required in the form of dry pigment or paste 
ground in linseed oil; it shall be prepared in accordance with the 
most improved methods. Grinding in oil shall be thorough and 
the vehicle shall be pure raw linseed oil. 

The material shall be bought by net weight. 

(a) Dry PicGMENT.—The pigment shall be a hydrated oxide of 
iron permeating a siliceous base, and shall be free from added 
impurities. It shall conform to the following requirements: 

Color—Color Strength—T one.—Equal to sample mutually agreed 
on by buyer and seller. 


Maximum | Minimum 


Per cent Per cent 


Coarse particles: Retained on standard No. 325 screen..............------------- ro) eg oe ea Be BE 
I sd 5 aed a an rash ep Mae Enc ote ee an ees dc mantis dee 17 
PAID Fas n tod Fina Cbs hin SOs ac BM Oe A tale bo okie FUR Ba ga EA Age ME Rs «FEE OS -linb tan. geses 
RiOMAS CMATURIINIG 2 5 olen bo. eens t IE. 54 4 a td A Pe Wone |S ests. 
iitena a Celeet Ss fi sesso Ye Mile 2 eae he re ae Wone sets. 23sza5. 


109839°—22 


2 Circular of the Bureau of Standards 


(b) Paste.—Ocher in paste form shall consist of: 


ea aera a erence ce ee ee es 


Maximum | Minimum 


Per cent Per cent 


Plemenit «02+ snc aged ckcbea cae aa eee a eee ees 71 
Linseed off o.c5 ws ceccacescnn gels he stoves tian «Gk mecns «ane iain ele oe tena veisie Asari 31 29 
Moisture and volatile matter... .-.-.---------- eee see eee eee eee eee eect errr teen nees 1 Fs Yas Spe poy ae eS 
Coarse particles and “skins” (total residue left on No. 325 screen) based on pig- 

TET. oo ee. Se enc ce uo od we Aiea 5m kw ea wich cre BPI tale Siw TARO mea Oia rn olathe el ee 9.5 \ecge a eee 


NotEe.—Deliveries will, in general, be sampled and tested by the following methods, but the purchaser 
reserves the right to use any additional available information to ascertain whether the material meets the 
specification. 


2. SAMPLING 


It is mutually agreed by buyer and seller that a single package 
out of each lot of not more than 1000 packages shall be taken 
as representative of the whole. 

With the dry pigment, this package shall be opened by the 
inspector and a sample of not less than 5 pounds taken at random 
from the contents and sent to the laboratory for test. 

With the paste, whenever possible, an original unopened con- 
tainer shall be sent to the laboratory; and when this is for any 


reason not done, the inspector shall determine, by thorough test- 


ing with a paddle or spatula, whether the material meets the 
requirement regarding not caking in the container. (See 4 (@).) 
He shall then thoroughly mix the contents of the container and 
draw a sample of not less than 5 pounds. This sample shall be — 
placed in a clean, dry, metal or glass container which it must 
nearly fill. The container shall be closed with a tight cover, sealed, 
marked, and sent to the laboratory for test with the inspector’s 
report on caking. 

When requested, a duplicate sample may be taken from the 
same package and delivered to the seller, and the inspector may 
take a third sample to hold for test in case of dispute. 


3. LABORATORY EXAMINATION OF DRY PIGMENT 


(2) COLOR AND TONE.—Weigh 1 g each of the color and stand- 
ard and rub up separately on a glass plate or stone slab, using 
the same amount of bleached linseed oil in each case. Place por- 
tions of each side by side on a clean strip of glass, turn the glass 
over and compare the colors. Rubbing up (mixing with oil) is 
best done with a muller, and should be such that no lumps remain 
and that the consistency of both paste portions is the same. 


Specification for Ocher, Dry and Paste ) 3 


Smear (with the finger) portions of the pastes on a clear glass 
strip and compare the tone by transmitted light. 

(6) CoLor STRENGTH.—Weigh accurately 0.05 g each of the 
color and standard and two portions of 1 g each of the zinc oxide. 
Add the color to one of the portions of zinc oxide and the standard 
to the other and rub up separately in linseed oil until on spreading 
out no dark streaks are visible. Place the color and standard tints 
side by side on a clean glass strip, turn the strip over and compare. 

(c) COARSE ParTICLES.‘—Dry in an oven at 105 to 110° C a 
325 screen, cool and weigh accurately. Weigh 10 g of the sample; 
dry at 100°C, transfer to a mortar, add 100 cc kerosene, thoroughly 
mix by gentle pressure with a pestle to break up all lumps; wash 
with kerosene through the screen, breaking up all lumps but not 
grinding. After washing with kerosene until all but the particles 
which are too coarse to pass the screen have been washed through, 
wash all kerosene from the screen with ether or petroleum ether, 
heat the screen for one hour at 105 to 110° C, cool and weigh. | 

(dq) MoisturE.—Place 1 g of the sample in a wide-mouth, short 
weighing tube provided with a glass stopper, and weigh accu- 
rately. Heat with stopper removed for two hours at a tempera- 
ture between 100 and 105° C. Insert stopper, cool and weigh. 
Calculate loss in weight as moisture. 

(€) ORGANIC COLORING MATTER (A. S. T. M. “Standards,” 1918, 
p. 656).—Test the pigment successively with hot water, 95 per 
cent alcohol, alcoholic sodium hydroxide and acetic acid. Chloro- 
form, sodium hydroxide, sulphuric acid, hydrochloric acid-stan- 
nous chloride solution, and other reagents may be tried. The 
solutions should remain colorless. The presence of an organic 
color may often be detected by the characteristic odor given off 
on ignition. 

(7) Tora, [Ron OxipE.—Ignite 1 g of the sample in a porcelain 
crucible at a dull red heat to destroy organic matter. Transfer to 
a 500 cc Erlenmeyer flask and add 20 cc of 1 : 1 hydrochloric acid. 
Digest just short of boiling until no dark specks can be seen in the 
insoluble residue. When the residue is light in color, the solution 
of iron may be considered complete. Dilute to 100 ce and without 
filtering, add 3 g of granulated zinc; put a funnel in the neck of 
the flask and heat when the action slackens; if basic iron salts 
separate out, add a few drops of hydrochloric acid. When the 


1 For a general discussion of screen tests of pigments and data regarding many pigments on the 
market, see Circular No. 148 of the Educational Bureau, Scientific Section, Paint ape cides eases Associa- 
tion of the U. S. 


4 Circular of the Bureau of Standards 


reduction is complete, add 30 cc of sulphuric acid (1 :2) and as 
soon as the residual zinc is dissolved, wash down the funnel and 
neck of the flask with a fine jet of water. Now add 200 cc of cool 
water and 30 ce of titrating solution (see reagents) and titrate 
with standard potassium permanganate. Run a blank on the 
zinc and calculate ferric oxide (Fe,O,). Any other accurate 
method for determining iron may be used at the option of the 
analyst. 

(9) Test FoR LEAD AND CALCIUM BY THE USUAL QUALITATIVE 
Meruops.—If calcium is present in appreciable amount, determine 
it as follows: Ignite 2.5 g in a porcelain crucible at a dull red heat 
to destroy organic matter. Transfer to a 500 cc graduated flask; 
add 100 cc of 1 : 1 hydrochloric acid. Digest just short of boiling 
until no dark specks can be seen in the insoluble residue; add 
ammonia in slight excess and about 2 cc of hydrogen peroxide 
solution; cool, dilute to 500 cc; mix thoroughly, filter through a 
dry paper. Take 100 cc of the filtrate (corresponding to 0.5 g 
of sample), heat to boiling, add a few drops of ammonia and an 
excess of a hot saturated ammonium oxalate solution. Continue 
boiling until the precipitate becomes granular; let stand about 
30 minutes, filter, wash with hot water until free from ammonium 
oxalate. Pierce the apex of the filter with a stirring rod and 
wash the precipitate into the beaker with hot water; pour warm 
dilute sulphuric acid (1 : 4) through the paper and wash a few 
times. Add about 30 cc of sulphuric acid (1 : 4), dilute to about 
250 ce with hot water and titrate at once with standard potas- 
sium permanganate solution (the solution should not be below 
60° C when the end point is reached). Calculate to CaO. (The 
Fe value of KMnO,X0.502 =CaO value.) 


4. LABORATORY EXAMINATION OF PASTE 


(a) CAKING IN CONTAINER.—When an original package is 
received in the laboratory it shall be weighed, opened, and stirred 
with a stiff spatula or paddle. The paste must be no more diffi- 
cult to break up and show no more caking than a normal good 
grade of ocher paste. The paste shall be finally thoroughly mixed, 
removed from the container, and the container wiped clean and 
weighed. ‘This weight subtracted from the weight of the original 
package gives the net weight of the contents. A portion of the 
thoroughly mixed paste shall be placed in a clean container and 
portions for the remaining tests promptly weighed out from it. 


Specification for Ocher, Dry aud Paste 5 


(6) MIxINc WITH OIL, or THINNING.—Add sufficient linseed 
oil to 100 g of the sample to make a liquid paint of proper con- 
sistency for application with a brush, noting the amount of oil 
necessary. Note the smoothness with which the paint works _ 
under the brush. 3 

(c) MoIstuRE AND OTHER VOLATILE MatTrer.—Weigh accu- 
rately from 3 to 5 g of the paste into a tared flat-bottomed dish 
about 5 cm in diameter, spreading the paste over the bottom. 
Heat at 105 to rro° C for one hour, cool, and weigh. Calculate 
loss in weight as percentage of moisture and volatile matter. 

(qd) PERCENTAGE OF PIGMENT.—Weigh accurately about 15 g 
of the paste into a weighed centrifuge tube. Add 20 to 30 cc of 
‘extraction mixture’’ (see Reagents), mix thoroughly with a glass 
rod, wash the rod with more of the extraction mixture, and add 
sufficient of the reagent to make a total of 60 cc in the tube. 
Place the tube in the container of a centrifuge, surround with 
water, and counterbalance the container of the opposite arm 
with a similar tube or a tube with water. Whirl at a moderate 
speed until well settled. Decant the clear supernatant liquid. 
Repeat the extraction twice with 4o cc of extraction mixture and 
once with 40 cc of ether. After drawing off the ether, set the 
tube in a beaker of water at about 80° C or on top of a warm 
oven for 10 minutes, then in an oven at 110 to 115° C for two 
hours. Cool, weigh, and calculate the percentage of pigment. 

(¢) EXAMINATION OF THE PIGMENT.—Grind the pigment from 
(d) to a fine powder, pass through an 80-mesh screen to remove 
any skins, preserve in a stoppered bottle, and examine as under 
3(e), 3(7), and 3(g). 

(7) CoLor, TONE, AND COLOR STRENGTH.—Extract the pig- 
ment from the vehicle with extraction mixture as in 4(d), except 
that it is not necessary to accurately weigh the amount taken, 
and after washing with ether, dry in a vacuum at a temperature 
not above 70° C. Grind this extracted pigment fine enough to 
pass a No. 80 screen to remove skins, and test as under 3(a) 
and 3(b). 

(g) COARSE PaRTICLES AND SKINS.—Weigh an amount of paste 
containing 10 g of pigment (see 4(d)), add 200 cc of kerosene, 
and wash through a No. 325 screen as in 3(c). 

(h) PREPARATION OF Farry Acips.—To about 25 g of the paste 
in a porcelain casserole, add 15 cc of aqueous sodium hydroxide 
(see reagents) and 75 cc of ethyl alcohol, mix and heat uncovered 


Ee ee << Se 


6 Circular of the Bureau of Standards 


e 


on a steam bath until saponification is complete (about one 
hour). Add 100 ce of water, boil, add sulphuric acid of specific 
gravity 1.2 (8 to 10 ce in excess), boil, stir, and transfer to a 
separatory funnel to which some water has been previously 
added. Draw off as much as possible of the acid aqueous layer 
and insoluble mineral matter, wash once with water, then add 
50 cc of water and 50 cc of ether. Shake very gently with a 
whirling motion to dissolve the fatty acids in the ether, but 
not so violently as to form an emulsion. Draw off the aqueous 
layer and wash the ether layer with one 15 cc portion of water 
and then with 5 cc portions of water until free from sulphuric 
acid, Then draw off the water layer completely. Transfer the 
ether solution to a dry flask and add 25 to 50 g anhydrous 
sodium sulphate. Stopper the flask and let stand with occasional 
shaking at a temperature below 25° C until the water is com- 
pletely removed from the ether solution, which will be shown by 
the solution becoming perfectly clear above the solid sodium 
sulphate. Decant this clear solution, if necessary, through a dry 
filter paper, into a dry 100 cc Erlenmeyer flask. Pass a rapid 
current of dry air (pass through a CaCl, tower) into the mouth of 
the Erlenmeyer flask and heat to a temperature below 75° C on 
a dry hot plate until the ether is entirely driven off. The fatty 
acids prepared as above should be kept in a stoppered flask and 
examined at once. 
Note. It is important to follow all of the details, since ether generally contains 
alcohol and, after washing with water, always contains water. It is very difficult to 
remove water and alcohol by evaporation from fatty acids, but the washing of the 
ether solution and subsequent drying with anhydrous sodium sulphate removes both 
water and alcohol. Ether, in the absence of water and alcohol, is easily removed 
from fatty acids by gentle heat. , 

(¢) TEST FoR MINERAL OIL AND OTHER UNSAPONIFIABLE MAT- 
TER.—Place 10 drops of the fatty acids (hk) in a 50 cc test tube, 
add 5 cc of alcoholic soda (see Reagents), boil vigorously for 5 
minutes, add 40 ce of water and mix; a clear solution indicates 
than not more than traces of unsaponifiable matter are present. 
If the solution is not clear, the oil is not pure linseed oil. 

(7) IopINE NUMBER oF Fatty Acips.—Place a small quantity 
of fatty acids (kh) in a small weighing burette or beaker. Weigh 
accurately. ‘Transfer, by dropping, about 0.15 g (0.10 to 0.20 g) 
to a 500 cc bottle having a well-ground glass stopper, or an Erlen- 
meyer flask having a specially flanged neck for the iodine test. 
Reweigh the burette or beaker and determine amount of sample 


Specification for Ocher, Dry and Paste 7 


used. Add 10 cc of chloroform. Whirl the bottle to dissolve 
the sample. Add 10 ce of chloroform to each of two empty 
bottles like that used for the sample. Add to each bottle 25 cc 
of the Hanus solution (see Reagents) and let stand, with occa- 
sional shaking, for one-half hour. Add 10 cc of the 15 per cent 
potassium iodide solution and 100 cc of water, and titrate with 
standard sodium thiosulphate using starch as indicator. The 
titrations on the two blank tests should agree within 0.1 cc. 
From the difference between the average of the blank titrations 
and the titration on the sample, and the iodine value of the thio- 
sulphate solution calculate the iodine number of the sample tested. 
(Iodine number is centigrams of iodine to 1 g of sample.) If the 
iodine number is less than 170, the oil does not meet the 
specification. 
5. REAGENTS 


(a) EXTRACTION MIxTURE.— 

10 volumes ether (ethyl ether). 
6 volumes benzol. 
4 volumes methyl alcohol. 
1 volume acetone. 

(6) AguEous Sopium HyproxipE.—Dissolve 100 g of sodium 
hydroxide in distilled water and dilute to 300 cc. 

(c) STANDARD SODIUM ‘THIOSULPATE SOLUTION. — Dissolve 
pure sodium thiosulphate in distilled water (that has been well 
boiled to free it from carbon dioxide) in the proportion of 24.83 g 
crystallized sodium thiosulphate to 1000 cc of the solution. It is 
best to let this solution stand for about two weeks before standard- 
izing. Standardize with pure resublimed iodine. (See Treadwell- 
Hall, Analytical Chemistry, vol. 2, 3d ed., p. 646.) This solution 
will be approximately decinormal, and it is best to leave it as it is 
after determining its exact iodine value, rather than to attempt 
to adjust it to exactly decinormal. Preserve in a stock bottle 
provided with a guard tube filled with soda lime. 

(d) STARCH SOLUTION.—Stir up 2 to 3 g of potato starch or 
5 g of soluble starch with roo cc of 1 per cent salicylic acid solution, 
add 300 to 400 cc boiling water, and boil the mixture until the 
starch is practically dissolved, then dilute to 1 liter. 

(ec) Porassrum IopripE SoL_uTION.—Dissolve 150 g of potassium 
iodide free from iodate in distilled water and dilute to 1000 cc. 

(7) Hanus So_urton.—Dissolve 13.2 g of iodine in 1000 cc of 
99.5 per cent glacial acetic acid, which will not reduce chromic 


8 Circular of the Bureau of Standards 


acid. Add enough bromine to double the halogen content, 
determine by titration (3 cc of bromine is about the proper 
amount). The iodine may be dissolved by the aid of heat, but 
the solution should be cold when the bromine is added. 

(g) ALCOHOLIC SopruM HyDROXIDE SOLUTION. —Dissolve pure 
sodium hydroxide in 95 per cent ethyl alcohol in the proportion 
of about 22 g per 1000 cc. Let stand in a stoppered bottle. 
Decant the clear liquid into another bottle and keep well stoppered. 
This solution should be colorless or only slightly yellow when used, 
and it will keep colorless longer if the alcohol is previously treated 
with sodium hydroxide (about 80 g to 1000 cc), kept at about 
50° C for 15 days, and then distilled. 

(h) POTASSIUM PERMANGANATE SOLUTION. —Dissolve 5.7 g of 
pure potassium permanganate in a liter of distilled water, let 
stand 8 to 14 days, siphon off the clear solution (or filter through 
an asbestos filter), and standardize as follows: In a 400 cc beaker 
dissolve 0.40 to 0.50 g of Bureau of Standards’ sodium oxalate 
in 250 cc of hot water (80 to 90° C) and add 15 ce of dilute sul- 
phuric acid (1:1). ‘Titrate at once with the potassium perman- 
ganate solution, stirring the liquid vigorously and continuously. 
The permanganate must not be added more rapidly than 10 to 15 
ce per minute, and the last 0.5 to 1 ce must be added dropwise 
with particular care to allow each drop to be fully decolorized 
before the next is introduced. ‘The solution should not be below 
60° C by the time the end point is reached. (Too rapid cooling 
may be prevented by allowing the beaker to stand on a small 
asbestos-covered hot plate during the titration. The use of a small 
thermometer as a stirring rod is most convenient.) The weight 
of sodium oxalate used multiplied by 0.8334 gives its iron equiva- 
lent. The permanganate solution should be kept in a glass 
stoppered bottle painted black to keep out light. 

(c) ‘TrTRATING SOLUTION.—Dissolve 160 g of manganese sul- 
phate in water, dilute to 1750 cc, add 330 cc of orthophosphoric acid 
(specific gravity 1.72), and 320 cc of concentrated sulphuric acid. 


ADDITIONAL COPIES 
OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 
AT . 
5 CENTS PER COPY 


V 


Tees 


DEPARTMENT OF COMMERCE 


BUREAU OF STANDARDS 


S. W. STRATTON, Director 


CIRCULAR OF THE BUREAU OF STANDARDS 


No. 93 


[2d edition, Issued June 21, 1922] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
IRON-OXIDE AND IRON-HYDROXIDE PAINTS 


FEDERAL SPECIFICATIONS BOARD 
STANDARD SPECIFICATION No. 13 


This Specification was officially adopted by the Federal Specifications Board, on 
February 3, 1922, for the use of the Departments and Independent Establishments 
of the Government in the purchase of materials covered by it. 


CONTENTS 

Page 
i a ie dive gl) se hws uae bin ik oo ado DE vp lk Gee I 
aie Ee gin dnd Sac p Ho inate Bie Gee darkness bw a 3 
Be porary Examination—Semipaste 00... ce cee dee est lees tar as nsaeas 3 
SE MINIM Ce) ee as, Ss ee ged has ee de a ee 6 
Re Lavoratory examimation—Mixed paint... -.. 0. le eee ee eck 7 
RPM PENNS hie sr) ie ete, A, NOU dd ened ee ALS ae 8 

1. GENERAL 


This specification applies to iron-oxide and iron-hydroxide 
paints of red and brown colors. The paint may be ordered in the 
form of either semipaste paint or ready-mixed paint. 

The basis of purchase may be either by net weight or by volume 
(231 cubic inches to the gallon). 

(a) Picment.—The pigment in both semipaste and ready- 
mixed paint shall be very finely ground iron oxide, iron hydroxide, 
siliceous minerals or a mixture thereof, to which carbon pigment 
may be added, if necessary, to produce the required color. It 
must be free from organic coloring matter (dyes or lakes). ‘The 
pigment shall show on analysis not less than 30 per cent of ferric 

63912°—23 


2 Circular of the Bureau of Standards 


oxide (Fe,0,). ‘The total of the ferric oxide, insoluble siliceous 
matter, and loss on ignition shall be not less than 9o per cent. 

(b) Laqurp.—The liquid in semipaste paint shall be entirely 
pure raw or refined linseed oil; in ready-mixed paint it shall con- 
tain not less than 75 per cent pure raw linseed oil, the balance to 
be combined drier and thinner. The thinner shall be turpentine, 
volatile mineral spirits, or a mixture thereof. 

(c) Semrpaste.—Semipaste shall be made by thoroughly grind- 
ing the pigment with pure raw or refined linseed oil. 

The semipaste as received and three months thereafter shall be 
not caked in the container and shall break up readily in linseed 
oil to form a smooth paint of brushing consistency. It shall mix 
readily with linseed oil, turpentine, or volatile mineral spirits, or 
any combination of these substances, in all proportions without 
curdling. ‘The color and hiding power when specified shall be 
equal to that of a sample mutually agreed upon by buyer and 
seller. ‘[he weight per gallon shall be not less than 1314 pounds. 
The paste shall consist of: 


| 
Maximum | Minimum 


Per cent Per cent 


Plgmentt... 00 ccssccccccabssnscersvacescanstscchacsgadenssweue ass settee =e mmanae 72.0 68.0 
rite v0 00) | Ee a a Se een ERM AME Cree fy: Arce eo 32.0 28.0 
Moisture and other volatile matter........-----.------ 0-22 --- 2-2 seeee ee cine eee eee OF sce 
Coarse particles and “skins” (total residue retained on No. 325 screen based on | 
pigment) /..55.. 556.0 c ee selec cece eee eadee scene seen ns anes ee nes ee Seen er S25 aes 


(d) Reapy-MrxEp Parint.—Ready-mixed paints shall be well 
ground, shall not settle badly or cake in the container, shall be 
readily broken up with a paddle to a smooth uniform paint of good 
_ brushing consistency, and shall dry within 18 hours to a full oil 
gloss, without streaking, running, or sagging. The color and 
hiding power when specified shall be equal to those of a sample 
mutually agreed upon by buyer and seller. The weight per gallon 
shall not be less than 12 pounds. ‘The paint shall consist of: 


Maximum | Minimum 


Per cent Per cent 


Pigment, siag deco hups cbiew sc Puce ence enc s Ae eae ene caches he eae 57.0 53.0 
Liquid (containing at least 75 per cent linseed oil)...-..... e's Gowleucn de fae aoe ee 47.0 . 43.0 
Water. icc). ke Ee ed a a ces nw ce ean eeeeea es ee ee 0.5 (Mi. 2an 
Coarse particles and *‘skins”’ (total residue retained on No. 325 screen based on 

DICMENE) ob 5 ain.s oo bcs sow Sains © Mien. eaiain'h mo S's in’a ola aise SEN ed eee ciara nee eta ee 3.5 Woes wean 


NorTe.—Deliveries will, in general, be sampled and tested by the following methods, but the purchaser 
reserves Sin right to use any additional available information to ascertain whether the material meets the 
specification. 


Specification for Iron-Oxide and Iron-Hydroxide 3 


2. SAMPLING 


It is mutually agreed by buyer and seller that a single package 
out of each lot of not more than 1000 packages shall be taken as 
representative of the whole. Whenever possible an original un- 
opened container shall be sent to the laboratory, and when this is 
for any reason not done, the inspector shall determine by thorough 
testing with a paddle or spatula whether the material meets the 
requirement regarding caking in the container. He shall then 
thoroughly mix the contents of the container and draw a sample of 
not less than 5 pounds of the thoroughly mixed paint, place it ina 
clean, dry metal or glass container, which it shall nearly fill. The 
container shall be closed with a tight cover, sealed, marked, and 
sent to the laboratory for test with the inspector’s report on caking. 

When requested, a duplicate sample may be taken from the same 
package and delivered to the seller, and the inspector may take a 
third sample to hold for test in case of dispute. 


3. LABORATORY EXAMINATION—-SEMIPASTE 


(a) CAKING IN CONTAINER.—When an original package is re- 
ceived in the laboratory it shall be weighed, opened, and stirred 
with a stiff spatula or paddle. The paste must be no more diffi- 
cult to break up than a normal good grade of semipaste paint. 
The semipaste shail finally be thoroughly mixed, removed from 
the container, and the container wiped clean and weighed. ‘This 
weight subtracted from the weight of the original package gives 
the net weight of the contents. A portion of thoroughly mixed 
semipaste shall be placed in a clean container and the portions for 
the remaining tests promptly weighed out. 

(b) CoLor.—Place some of the paint on a clean, clear glass plate. 
Place some of the standard agreed upon beside the sample on the 
plate, turn the glass over, and compare the colors. 

(c) WEIGHT PER GALLON.—From the weight of a known volume 
of the paste calculate the specific gravity, which multiplied by 
8.33 gives the weight in pounds per gallon. Any suitable con- 
tainer of known volume may be used for the purpose, but a short 
cylinder of heavy glass with rounded bottom about 75 mm high 
and having a capacity of from 125 to 175 cc (a glass cap to keep 
dust from reagent bottle stopper) is a convenient apparatus for 
the purpose. ‘The capacity of this vessel is determined to within 
tcc. The paste is packed into it until completely full, the top 
leveled off smooth with a spatula, and weighed to +0.5 g. Sub- 


4 Circular of the Bureau of Standards 


tract the weight of the empty container and divide the remainder 
by the number of cubic centimeters representing the capacity of 
the container. The quotient is the specific gravity, which can be 
thus determined within +2 in the second decimal place. 

(d) Mrxinc witH LINSEED O1L.—One hundred grams of the 
paste shall be placed in a cup, 30 cc linseed oil added slowly, with 
careful stirring and mixing with a spatula or paddle. The result- 
ing mixture must be smooth and of good brushing consistency. 

(ec) MoIstuRE AND OTHER VOLATILE MATTER.—Weigh accu- 
rately from 3 to 5 g of the paste into a tarred flat-bottomed dish 
about 5 cm in diameter, spreading the paste over the bottom. 
Heat at 105 to 110° C for one hour, cool, and weigh. Calculate 
loss in weight as percentage of moisture and volatile matter. 

(f) PERCENTAGE OF PIGMENT.—Weigh accurately about 15 g of 
the paste into a weighed centrifuge tube. Add 20 to 30cc of 
‘“‘extraction mixture’’ (see Reagents), mix thoroughly with a glass 
rod, wash the rod with more of the extraction mixture, and add 
sufficient of the reagent to make a total of 60 ce in the tube. 
Place the tube in the container of a centrifuge, surround with 
water, and counterbalance the container of the opposite arm 
with a similar tube or a tube with water. Whirl at a moderate 
speed until well settled. Decant the clear supernatant liquid. 
Repeat the extraction twice with 40 ce of extraction mixture and 
once with 40 cc of ether. After drawing off the ether, set the 
tube in a beaker of water at about 80° C or on top of a warm oven 
for 10 minutes, then in an oven at 110 to 115° C for two hours. 
Cool, weigh, and calculate the percentage of pigment. Grind 
the pigment to a fine powder, pass through a No. 80 screen to re- 
move any skins, and preserve in a stoppered bottle. 

(g) PREPARATION OF Farry Acips.—To about 25 g of the paste 
in a porcelain casserole, add 15 cc of aqueous sodium hydroxide 
(see Reagents) and 75 cc of ethyl alcohol, mix and heat uncovered 
on a steam bath until saponification is complete (about one hour). 
Add 100 cc of water, boil, add sulphuric acid of specific gravity 1.2 
(8 to 10 cc in excess), boil, stir, and transfer to a separatory funnel 
to which some water has been previously added. Draw off as much 
as possible of the acid aqueous layer, wash once with water, then 
add 50 cc of water and 50 cc of ether. Shake very gently witha 
_ whirling motion to dissolve the fatty acids in the ether, but not so 
violently as to formanemulsion. Draw off the aqueous layer and 


Specification for Iron-Oxide and Iron-Hydroxide 5 


wash the ether layer with one 15 cc portion of water and then with 
5 ce portions of water until free from sulphuric acid. Then draw off 
the water layer completely. Transfer the ether solution to a dry 
flask and add 25 to 50 g of anhydrous sodium sulphate. Stopper 
the flask and let stand with occasional shaking at a temperature 
below 25° C. until the water is completely removed from the 
ether solution, which will be shown by the solution becoming 
perfectly clear above the solid sodium sulphate. Decant this 
clear solution, if necessary, through a dry filter paper, into a dry 
100 cc Erlenmeyer flask. Pass a rapid current of dry air (pass 
through a CaCl, tower) into the mouth of the Erlenmeyer flask 
and heat to a temperature below 75° C on a dry hot plate until 
the ether is entirely driven off. 

 Nors.—It is important to follow all of the details, since ether generally contains 
alcohol and after washing with water always contains water. It is very difficult 
to remove water and alcohol by evaporation from fatty acids, but the washing of the 
ether solution and subsequent drying with anhydrous sodium sulphate removes both 
water and alcohol. Ether, in the absence of water and alcohol, is easily removed 
from fatty acids by gentle heat. 

The fatty acids prepared as above should be kept in a ee 
flask and examined at once. 

(h) Test FOR MINERAL OIL, AND OTHER UNSAPONIFIABLE 
MATTER.—Place 10 drops of the fatty acid (g) in a 50 cc test 
tube, add 5 cc of alcoholic soda (see reagents), boil vigorously 
for five minutes, add 40 cc of water, and mix; a clear solution 
indicates that not more than traces of unsaponifiable matter are 
present. If the solution is not clear, the oil is not pure linseed oil. 

(2) lopinE NuMBER oF Farry Acips.—Place a small quantity 
of the fatty acids (g) in a small weighing burette or beaker. Weigh 
accurately. ‘Transfer by dropping about 0.15 g (0.10 to 0.20 g) 
into a 500 cc bottle having a well-ground glass stopper, or art 
Erlenmeyer flask having a specially flanged neck for the iodine 
test. Reweigh the burette or beaker and determine amount of 
sample used. Add 10 cc of chloroform. Whirl the bottle to dis- 
solve the sample. Add 10 ce of chloroform to two empty bottles 
like that used for the sample. Add to each bottle 25 cc of the 
Hanus solution (see reagents) and let stand with occasional 
shaking for one-half hour. Add 10 cc of the 15 per cent potassium 
iodide solution and 100 cc of water, and titrate with standard 
sodium thiosulphate, using starch as indicator. The titrations 
on the two blank tests should agree within 0.1 cc. From the 
difference between the average of the blank titrations and the 


6 Circular of the Bureau of Standards 


titration on the sample and the iodine value of the thiosulphate 
solution, calculate the iodine number of the sample tested. (Iodine 
number is centigrams of iodine to 1 g of sample.) If the iodone 
number is less than 170, the oil does not meet the specification. 

) CoARSE PARTICLES AND SKINS.—Dry in an oven at 105 to 
110° C a No. 325 screen, cool, and weigh accurately. Weigh an 
amount of semipaste containing 10 g of pigment (see 3 (f)), add 
50 cc of kerosene, mix thoroughly, and wash with kerosene 
through the screen, breaking up all lumps, but not grinding. 
After washing with kerosene until all but the particles too coarse 
to pass the screen have been washed through, wash all kerosene 
from the screen with ether or petroleum ether, heat the; screen for 
one hour at 105 to 110° C, cool, and weigh. : tothe o03 


4. ANALYSIS OF PIGMENT 


(a) OrcANric CoLorinc Marrer.—(A. S. T. M. Standards, 1918, 
p. 656). Test the pigment successively with hot water, 95 per cent 
alcohol, alcoholic sodium hydroxide, and acetic acid. Chloroform, 
sodium hydroxide, sulphuric acid, hydrochloric acid-stannous 
chloride solution, and other reagents may be tried. The solutions 
should remain colorless. ‘The presence of an organic color may 
often be detected by the characteristic odor given off on ignition. 

(b) Tora, IRoN OxmpE.—Ignite 1 g of the pigment in a porce- 
lain crucible at a dull red heat to destroy organic matter. Trans- 
fer to a 500 cc Erlenmeyer flask and add 20 ce of 1:1 hydro- 
chloric acid. Digest just short of boiling till no dark specks can 
be seen in the insoluble residue. When the residue is light in 
color, the solution of iron may be considered complete. Dilute 
to 100 cc and without filtering, add 3 g of granulated zinc; put a 
funnel in the neck of the flask and heat when the action slackens; 
if basic iron salts separate out, add a few drops of hydrochloric 
acid. When the reduction is complete, add 30 cc of sulphuric 
acid (1:2), and as soon as the residual zine is dissolved, wash 
down the funnel and neck of the flask with a fine jet of water. 
Now add 200 ce of cool water and 30 cc of titrating solution (see 
reagents) and titrate with standard potassium permanganate. 
Run a blank on the zine and calculate iron as Fe,O,. Any other 
accurate method for determining iron may be used at the option 
of the analyst. 

(c) Loss on IGniTION.—Ignite 1 g of the pigment to constant 
weight. It is safest to use a porcelain crucible for this purpose. 


Specification for Iron-Oxide and Iron-Hydroxide 7 


(qd) INSOLUBLE SILICEOUS MaTTrEeR.—Transfer 1 g of the pig- 
ment to a porcelain dish, ignite at a dull red heat to destroy 
organic matter, cool, add 20 cc of hydrochloric acid, 1: 1, cover 
and heat on a steam bath until no dark specks can be seen in 
the insoluble residue. Remove cover, add 10 cc of strong hydro- 
chloric acid, evaporate to dryness on a steam bath, moisten with 
hydrochloric acid, add water, and wash on to a filter paper with 
hot water; wash, ignite, and weigh the insoluble siliceous matter. 


5. LABORATORY EXAMINATION—MIXED PAINT 


(a) CAKING IN CONTAINER.—Follow the procedure outlined in 
3(a), noting that the paint should be no more difficult to break ES 
than a good grade of mixed paint. 

(6) CoLor.—Follow the procedure outlined in 3(b). 

(c) WEIGHT PER GALLON.—Weigh a clean, dry, 100 cc gradu- 
ated flask. Fill to the mark with the thoroughly mixed paint and 
weigh again. The increase in weight expressed in grams, divided 
by 100, gives the specific gravity, which multiplied by 8.33 gives 
the weight in pounds per gallon. 

(d) BRUSHING PROPERTIES AND TIME OF DRYING.—Brush the 
well-mixed paint on a suitable panel, which may be ground glass, 
steel, or well-filled wood. Note whether the paint works satis- 
factorily under the brush. Place the panel in a vertical position 
in a well-ventilated room and let stand for 18 hours. The paint 
shall be dry, smooth, and free from streaks. 

(e) WaTER.—Mix 100 g of the paint in a 300 cc flask with 75 ce 
of toluol. Connect with a condenser and distill until about 50 ce 
of distillate has been collected in a graduate. The temperature in 
the flask should be then about 105 to 110° C. The number of 
cubic centimeters of water collecting under the toluol in the re- 
ceiver is the percentage of water in the paint. Material com- 
plying with the specification should yield less than 0.5 cc. 

(f) VOLATILE THINNER.—Follow the procedure outlined in 
3(e). Correct the result for any water found (see 5(e)) and report 
the remainder as volatile thinner. 

(g) PERCENTAGE OF PIGMENT.—Follow the procedure outlined 
in 3(7). 

(h) TESTING NONVOLATILE VEHICLE.—Follow the procedure 
outlined in 3(g), 3(h), and 3(2), except that in the preparation of 
the fatty acids the mixture of paint and alkali is heated on the 
steam bath until all volatile thinner is driven off. 


8 Circular of the Bureau of Standards 


(1) CoaRSE PARTICLES AND Sxrns.—Follow the procedure out- 
lined in 3(7). 
(j) Testinc Prcment.—Follow the procedure outlined in 4(a) 
to 4(d), inclusive. 
6. REAGENTS 


(a) EXTRACTION MIXTURE.— 
10 volumes ether (ethyl ether). 
6 volumes benzol. 
4 volumes methyl] alcohol. 
I volume acetone. 


(b) AguEous SopruM HyproxIpE.—Dissolve 100 g of sodium 
hydroxide in distilled water and dilute to 300 ce. 

(c) STANDARD SODIUM THIOSULPHATE SOLUTION.—Dissolve pure 
sodium thiosulphate in distilled water (that has been well boiled 
to free it from carbon dioxide) in the proportion of 24.83 g of 
crystallized sodium thiosulphate to 1000 ee of the solution. It 
is best to let this solution stand for about two weeks before 
standardizing. Standardize with pure resublimed iodine. (See 
Treadwell-Hall, Analytical Chemistry, vol. 2; 3d ed., p. 646.) 
This solution will be approximately decinormal, and it is best to 
leave it as it is after determining its exact iodine value, rather 
than to attempt to adjust it to exactly decinormal. Preserve 
in a stock bottle provided with a guard tube filled with soda lime. 

(d) STaRcH SOLUTION.—Stir up 2 to 3 g of potato starch or 5 g 
of soluble starch with 100 ce of 1 per cent salicylic acid solution, 
add 300 to 400 cc boiling water, and boil the mixture until the 
starch is practically dissolved, then dilute to 1 liter. 

(e) Porasstum IopIDE SOLUTION.—Dissolve 150 g of potassium 
iodide free from iodate in distilled water and dilute to 1000 cc. 

(f) HANuUS SoLuTION.—Dissolve 13.2 g of iodine in 1000 cc of 
99.5 per cent glacial acetic acid, which will not reduce chromic 
acid. Add enough bromine to double the halogen content, 
determined by titration (3 cc of bromine is about the proper 
amount). ‘The iodine may be dissolved by the aid of heat, but 
the solution should be cold when the bromine is added. 

(g) ALCOHOLIC SODIUM HYDROXIDE SOLUTION.—Dissolve pure 
sodium hydroxide in 95 per cent ethyl alcohol in the proportion 
of about 22 g per 1000 cc. Let stand in a stoppered bottle. 
Decant the clear liquid into another bottle and keep well stoppered. 
This solution should be colorless or only slightly yellow when used, 


Specification for Iron-Oxide and Iron-H ydroxide 9 


and it will keep colorless longer if the alcohol is previously treated 
with sodium hydroxide (about 80 g to 1000 cc), kept at about 
50° C for 15 days, and then distilled. 

(h) PoTasstumM PERMANGANATE SOLUTION.—Dissolve 5.7 g of 
pure potassium permanganate in a liter of distilled water, let stand 
8 to 14 days, siphon off the clear solution (or filter through an 
asbestos filter), and standardize as follows: In a 400 cc beaker 
dissolve 0.40-0.50 g of Bureau of Standards’ sodium oxalate in 
250 cc of hot water (80 to 90° C) and add 15 cc of dilute sulphuric 
acid (1:1). ‘Titrate at once with the potassium permanganate 
solution, stirring the liquid vigorously and continuously. ‘The per- 
manganate must not be added more rapidly than Io to 15 ce per 
minute, and the last 0.5 to 1 cc must be added dropwise with 
particular care to allow each drop to be fully decolorized before 
the next is introduced. ‘The solution should not be below 60° C 
by the time the end point is reached. (More rapid cooling may 
be prevented by allowing the beaker to stand on a small asbestos- 
covered hot plate during the titration. The use of a small ther- 
mometer as a stirring rod is most convenient.) The weight of 
sodium oxalate used multiplied by 0.8334 gives its iron equiva- 
lent. The permanganate solution should be kept in a glass- 
stoppered bottle painted black to keep out light. 

(4) TrTRATING SOLUTION.—Dissolve 160 g of manganese sul- 
phate in water, dilute to 1750 cc, add 330 cc of orthophosphoric acid 
(specific gravity 1.72), and 320 cc of concentrated sulphuric acid. 


ADDITIONAL COPIES 
OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 
AT 
5 CENTS PER COPY 


V 


DEPARTMENT OF COMMERCE. 
BUREAU OF STANDARDS. 


S. W. STRATTON, Director. 


CIRCULAR OF THE BUREAU OF STANDARDS. 


No. 94. 


[2d edition. Issued July 7, 1922.] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
BLACK PAINT, SEMIPASTE AND READY MIXED. 
FEDERAL SPECIFICATIONS BOARD. 


STANDARD SPECIFICATION. NO. 14. 
This Specification was officially adopted by the Federal Specifications Board on 


February 3, 1922, for the use of the Departments and Independent Establish- 
ments of the Government in the purchase of materials covered by it. 


CONTENTS. | 

Page. 
Re RI ete Lime sabe oe gre wri atane acquoivcg en sote wow acum pcs tia a vlcbeee os SE 
a ERIE Se Te ook shee ew gine ou tea pes K3 
3. Laboratory examination—Semipaste............ 00. cc ec ce cece ccc eeceeeeees 3 
tees erientsy oi)... ee. a os gud alee i asta ate 6 
5. Laboratory examination—Mixed paint .......... 0... cc cece eee eeeeecees 7 
Re Bee a od Nes fog seg Uagereimn ds ht ok wee hak ee 8 


1. GENERAL. 


Black paint may be ordered in the form of either semipaste 
paint or ready-mixed paint. , 

The basis of purchase may be either by net weight or by 
volume (231 cubic inches to the gallon). 

(a) Picment.—The pigment in both semipaste and ready- 
mixed paints shall consist of carbon, lead oxide, insoluble mineral 
material, and, at the option of the manufacturer, oxide of iron. 
The pigment shall show on analysis not less than 20 per cent of 
carbon and not less than 5 per cent of lead oxide calculated as 


Additional copies of this publication may be procured from the Superintendent of Documents, Gov- 
ernment Printing Office, Washington, D. C., at 5 cents per copy. 


106567 °—24 


2 Circular of the Bureau of Standards 


Pb,O,. The total of the lead oxide, iron oxide, insoluble siliceous 
material, and loss on ignition shall be not less than 90 per cent. 

(b) Liourp.—The liquid in semipaste paint shall be entirely 
pure raw or refined linseed oil; in ready-mixed paint it shall con- 
tain not less than 80 per cent pure raw linseed oil, the balance to — 
be combined drier and thinner. ‘The thinner shall be turpentine, 
volatile mineral spirits, or a mixture thereof. 

(c) SEMIpASTE.—Semipaste shall be made by thoroughly grind- 
ing the pigment with pure raw or refined linseed oil. 

‘The semipaste as received and three months thereafter shall be 
not caked in the container and shall break up readily in linseed 
oil to form a smooth paint of brushing consistency. It shall mix 
readily with linseed oil, turpentine, or volatile mineral spirits, or 
any combination of these substances, in all proportions without 
curdling. ‘The color and hiding power when specified shall be 
equal to that of a sample mutually agreed upon by buyer and 
seller. The weight per gallon shall be not less than 10 pounds. 
The paste shall consist of: 


Maximum.| Minimum. 


PISMO. oo i cae s nce cen ack ne sins bia wee nale vw ea.e'e os palaripin ee arms gw iy eee 48 
Tansee OF) 2, oo og ncaie widvase ois.a s ofp ov & pierw 0 0/0055, a:0/4:0.0 060 6p 016 9 '> m mY Oslo aiale alee ata eee 52 48 
Moisture and other volatile matter ........ 0.02. cece eect entre ett tence et scans DoF tesutseecuas 
Coarse particles and “‘skins”’ (total residue retained on No. 325 screen based on 


Mr ettt) os os cdc Ua cs pc re bbe 0 a be wna veo alee nm en le ohare gee Le Och i ete easter 


(d) Reapy-Mixep Parnt.—Ready-mixed paint shall be well 
ground, shall not settle badly or cake in the container, shall be 
readily broken up with a paddle to a smooth uniform paint of good 
brushing consistency, and shall dry within 18 hours to a full oil 
gloss, without streaking, running, or sagging. The color and 
hiding power when specified shall be equal to those of a sample — 
mutually agreed upon by buyer and seller. The weight per gallon 
shall be not less than 9 pounds. ‘The paint shall consist of: | 


Maximum.) Minimum, 


Ui Sasa 1 ene ea Ce oO SE pier n ee tie Mines Re MEME AN TERT er Lk 
Liquid (containing at least 80 per cent linseed oil)........... 0... 00s cece eee eee 72 68 
WAR BT er OURS al ae ac Gen a et IC re Coke Ca tek ts UC ah weshts he srs 0,3 ickenceny ain 
Coarse particles and ‘“‘skins”’ (total residue retained on No. 325 screen based on 


SEES oa Say sins Gclcvp 5.0 Wom OED RA DID RR Res ae Mies eh dace ge LG leew tuacebes 


Notr.—Deliveries will, in general, be sampled and tested by the following methods, 
but the purchaser reserves the right to use any additional available information te 
ascertain whether the material meets the specification. | 


Specification for Black Patwnt 3 
2. SAMPLING. 


It is mutually agreed by buyer and seller that a single package 
out of each lot of not more than 1,000 packages shall be taken as 
representative of the whole. Whenever possible an original 
unopened container shall be sent to the laboratory, and when this . 
is for any reason not done, the inspector shall determine by 
thorough testing with a paddle or spatula whether the material 
meets the requirements regarding caking in the container. He © 
shall then thoroughly mix the contents of the container and draw 
a sample of not less than 5 pounds of the thoroughly mixed paint, 
place it in a clean, dry metal or glass container, which it shall 
nearly fill. The container shall be closed with a tight cover, 
sealed, marked, and sent to the laboratory for test with the 
inspector’s report on caking. , 

When requested, a duplicate sample may be taken from the same 
package and delivered to the seller, and the inspector may take a 
third sample to hold for test in case of dispute. 


3. LABORATORY EXAMINATION—SEMIPASTE. 


(a) CAKING IN CONTAINER.—When an original package is 
received in the laboratory it shall be weighed, opened, and stirred 
with a stiff spatula or paddle. The paste must be no more diffi- 
cult to break up than a normal good grade of semipaste paint. 
_ The semipaste shall finally be thoroughly mixed, removed from 
the container, and the container wiped clean and weighed. This 
weight subtracted from the weight of the original package gives 
the net weight of the contents. A portion of thoroughly mixed 
_ semipaste shall be placed in a clean container and the portions for 
the remaining tests promptly weighed out. 

(b) CoLor.—Place some of the paint on a clean clear glass 
plate. Place some of the standard agreed upon beside the sample 
on the plate, turn the glass over, and compare the colors. 

(c) WEIGHT PER GALLON.—From the weight of a known volume 
of the paste calculate the specific gravity, which multiplied by 
8.33 gives the weight in pounds per gallon. Any suitable con- 
tainer of known volume may be used for the purpose, but a short 
cylinder of heavy glass with rounded bottom about 75 mm. high 
and having a capacity of from 125 to 175 cc (a glass cap to keep 
dust from reagent bottle stopper) is a convenient apparatus for 
the purpose. The capacity of this vessel is deternined to within 
Ice. The paste is packed into it until completely full, the top 


4 Circular of the Bureau oj Standards 


leveled off smooth with a spatula, and weighed to +0.5 g. Sub- 
tract the weight of the empty container and divide the remainder 
by the number of cubic centimeters representing the capacity of 
the container. ‘The quotient is the specific gravity, which can be 
thus determined within +2 in the second decimal place. 

(d) Mrxtnc wits LinsEED Ou.—One hundred grams of the 
paste shall be placed in a cup, 70 cc linseed oil added slowly with 
careful stirring and mixing with a spatula or paddle. ‘The result- 
ing mixture must be smooth and of good brushing consistency. 

(ec) MorstuRE AND OTHER VOLATILE MaTTER.—Weigh accu- 
rately from 3 to 5 g of the paste into a tared flat-bottomed dish 
about 5 cm in diameter, spreading the paste over the bottom. 
Heat at 105 to 110° C. for one hour, cool, and weigh. Calculate 
loss in weight as percentage of moisture and volatile matter. 

(f) PERCENTAGE OF PicMENT.—Weigh accurately about 15 g 
of the paste into a weighed centrifuge tube. Add 20 to 30 cc 
of ‘extraction mixture”? (see reagents), mix thoroughly with a 
glass rod, wash the rod with more of the extraction mixture, and 
add sufficient of the reagent to make a total of 60 cc in the tube. 
Place the tube in the container of a centrifuge, surround with 
water, and counterbalance the container of the opposite arm 
with a similar tube or a tube with water. Whirl at a moderate 
speed until well settled. Decant the clear supernatant liquid. 
Repeat the extraction twice with 40 cc of extraction mixture 
and once with 40 cc of ether. After drawing off the ether, set 
the tube in a beaker of water at about 80° C. or on top of a warm 
oven for 10 minutes, then in an oven at 110 to 115° C. for two 
hours. Cool, weigh, and calculate the percentage of pigment. 
Grind the pigment to a fine powder, pass through a No. 80 screen 
to remove any skins, and preserve in a stoppered bottle. | 

(g) PREPARATION OF Farry Actps.—To about 25 g of the paste 
in a porcelain casserole, add 15 cc of aqueous sodium hydroxide 
(see reagents) and 75 cc of ethyl alcohol, mix and heat un- 
covered on a steam bath until saponification is complete (about 
one hour). Add 100 ce of water, boil, add sulphuric acid of 
specific gravity 1.2 (8 to 10 cc in excess), boil, stir, and 
transfer to a separatory funnel to which some water has been 
previously added. Draw off as much as possible of the acid 
aqueous layer, wash once with water, then add 50 cc of water and 

occ of ether. Shake very gently with a whirling motion to dis- 
solve the fatty acids in the ether, but not so violently as to form 


» 


Specification for Black Paini 5 


an emulsion. Draw off the aqueous layer and wash the ether 
layer with one 15 cc portion of water and then with 5 cc portions 
of water until free from sulphuric acid. Then draw off the water 
layer completely. ‘Transfer the ether solution to a dry flask and 
add 25 to 50 g of anhydrous sodium sulphate. Stopper the flask 
and let stand with occasional shaking at a temperature below 
25° C. until the water is completely removed from the ether solu- 
tion, which will be shown by the solution becoming perfectly 
clear above the solid sodium sulphate. Decant this clear solution, 
if necessary, through a dry filter paper, into a dry 100 cc Erlen- 
meyer flask. Pass a rapid current of dry air (pass through a 
CaCl, tower) into the mouth of the Erlenmeyer flask and heat to 
a temperature below 75° C. on a dry hot plate until the ether is 
entirely driven off. 

NoTE.—It is important to follow all of the details since ether generally contains 
alcohol and after washing with water always contains water. It is very difficult 
to remove water and alcohol by evaporation from fatty acids, but the washing of the 
ether solution and subsequent drying with anhydrous sodium sulphate removes both 
water and alcohol. Ether, in the absence of water and alcohol, is easily removed 
from fatty acids by gentle heat. 

The fatty acids prepared as above should be kept in a stoppered 
flask and examined at once. | 

(h) Test FoR MINERAL Om, AND OTHER UNSAPONIFIABLE 
MaTTER.—Place 10 drops of the fatty acid (g) in a 50 cc test 
tube, add 5 cc of alcoholic soda (see reagents), boil vigorously 
for five minutes, add 40 cc of water, and mix; a clear solution 
indicates that not more than traces of unsaponifiable matter are 
present. If the solution is not clear, the oil is not pure linseed oil. 

(2) opine NuMBER oF Farry Actps.—Place a small quantity 
of the fatty acids (g) in a small weighing burette or beaker. Weigh 
accurately. ‘Transfer by dropping about 0.15 g (0.10 to 0.20 g) 
into a 500 cc bottle having a well-ground glass stopper, or an 
Erlenmeyer flask having a specially flanged neck for the iodine 
test. Reweigh the burette or beaker and determine amount of 
sample used. Add tocc of chloroform. Whirl the bottle to dis- 
solve the sample. Add 10 cc of chloroform to two empty bottles 
like that used for the sample. Add to each bottle 25 cc of the 
Hanus solution (see reagents) and let stand with occasional 
shaking for one-half hour. Add 1occ of the 15 per cent potassium 
iodide solution and 100 cc of water, and titrate with standard 
sodium thiosulphate, using starch as indicator. The titrations 
on the two blark tests should agree within 0.1 cc. From the 


6 Circular of the Bureau of Standards 


difference between the average of the blank titrations and the 
titration on the sample and the iodine value of the thiosulphate 
solution, calculate the iodine number of the sample tested. (Iodine 
number is centigrams of iodine to 1 g of sample.) If the iodine 
number is less than 170, the oil does not meet the specification. 

(7) CoarsH PARTICLES AND Sxins.—Dry in an oven at 105 to 
110° C. a No. 325 screen, cool, and weigh accurately. Weigh an 
amount of semipaste containing 10 g of pigment (see 3 (f)), add 
50 cc of kerosene, mix thoroughly, and wash with kerosene 
through the screen, breaking up all lumps but not grinding. After 
washing with kerosene until all but the particles too coarse to pass 
the screen have been washed through, wash all kerosene from the 
screen with ether or petroleum ether, heat the screen ror one 
hour at 105 to 110° C., cool, and weigh. 


4. ANALYSIS OF PIGMENT. 


(az) QuatitativE ANALysIs.—Make qualitative analysis follow- 
ing ordinary methods. 

(b) Loss on Icnrt10oN.—Ignite 1 g of the pigment in a weighed 
porcelain crucible until all carbon is consumed. It is best to use 
gentle heat with free access of air. Cool, weigh, and calculate 
the percentage of loss on ignition. 

(c) CARBON AND INSOLUBLE MINERAL MATERIAL.—Place 1 g 
of the pigment in a porcelain dish, moisten with a few drops of 
alcohol, add 20 cc of concentrated hydrochloric acid, cover, and 
heat on steam bath for 15 minutes. Remove cover and evaporate 
to dryness, moisten with hydrochloric acid, add 25 ce of water, 
filter on a weighed Gooch crucible, and wash with hot water until 
the washings are free from lead and iron. Dry the crucible and 
contents at 105 to 110° C. for 2 hours. Ignite for 7 minutes in a 
current of dry carbon dioxide (using a Rose crucible cover) with 
a flame about 20 cm high. Cool ina current of dry carbon dioxide 
and weigh. ‘Then ignite with free access of air (or in a current of 
oxygen) until all carbon is consumed. Cool and weigh. The loss 
in weight is calculated as carbon, and the residue remaining on 
the Gooch crucible is calculated as insoluble mineral material. 

(d) Leap OxIpDE AND IRON OxipE.—Determine lead and iron 
in the filtrate from the carbon determination by any convenient 
method, calculating lead to Pb,O, and iron to Fe,O,. | 


Specification for Black Paint 7 
5. LABORATORY EXAMINATION—MIXED PAINT. 


(a) CAKING IN CONTAINER.—Follow the procedure outlined in 
3(@), noting that the paint should be no more difficult to break up 
than a good grade of mixed paint. 

(6) Cotor.—Follow the procedure outlined in 3(b). 

(c) WEIGHT PER GAaLLON.—Weigh a clean, dry, 100 ce gradu- 
ated flask. Fill to the mark with tHe thoroughly mixed paint and 
weigh again. The increase in weight expressed in grams, divided 
by 100, gives the specific gravity, which multiplied by 8.33 gives 
the weight in pounds per gallon. 

(d) BRUSHING PROPERTIES AND Time oF Dryinc.—Brush the 

well-mixed paint on a suitable panel, which may be ground glass, 
steel, or well-filled wood. Note whether the paint works satis- 
factorily under the brush. Place the panel in a vertical position 
in a well-ventilated room and let stand for 18 hours. ‘The paint 
shall be dry, smooth, and free from streaks. 
— (e) WaTer.—Mix 100 g of the paint in a 300 cc flask with 
75 cc of toluol. Connect with a condenser and distill until about 
50 cc of distillate has been collected in a graduate. ‘The tempera- 
ture in the flask should be then about 105 to 110°C. ‘The number 
of cubic centimeters of water collecting under the toluol in the 
receiver is the percentage of water in the paint. Material com- 
plying with the specification should yield less than 0.5 cc. 

(7) VOLATILE THINNER.—Follow the procedure outlined in 3(e). 
Correct the result for any water found (see 5(e)) and report the 
remainder as a volatile thinner. 

(g) PERCENTAGE OF PiGMENT.—Follow the procedure outlined 
in 3 (7). 

(h) Testinc NoNVOLATILE VEHICLE.—Follow the procedure 
outlined in 3(g), 3(), and 3(2), except that in the preparation of 
the fatty acids the mixture of paint and alkali is heated on the. 
steam bath until all volatile thinner is driven off. 

(1) COARSE PARTICLES AND SKINS.—Follow the procedure out- 
lined in 3(9). 

(j) Testinc Picment.—Follow the procedure outlined in 4(a) 
to 4(d) inclusive. 


8 Circular of the Bureau of Standards 
6. REAGENTS. 


(a) EXTRACTION MIXTURE.— 

‘ro volumes ether (ethyl ether). 
6 volumes benzol. 
4 volumes methy] alcohol. 
1 volume acetone. 

(b) Aguzous Sop1um HyproxmeE.—Dissolve roo g of sodium 
hydroxide in distilled water and dilute to 300 cc. : 

(c) STANDARD SopruM THIOSULPHATE SOLUTION.—Dissolve pure 
sodium thiosulphate in distilled water (that has been well boiled 
to free it from carbon dioxide) in the proportion of 24.83 g of 
crystallized sodium thiosulphate to 1,000 cc. of the solution. 
It-is best to let this solution stand for about two weeks before 
standardizing. Standardize with pure resublimed iodine. (See 
Treadwell-Hall, Analytical Chemistry, vol. 2, 3d ed., p. 646.) 
This solution will be approximately decinormal, and it is best to 
leave it as it is after determining its exact iodine value, rather 
than to attempt to adjust it to exactly decinormal. Preserve 
in a stock bottle provided with a guard tube filled with soda lime. 

(d) StarcH SOLUTION.—Stir up 2 to 3 g of potato starch or 
5 g of soluble starch with 100 cc of 1 per cent salicyclic acid solu- 
tion, add 300 to 400 ce. boiling water, and boil the mixture until the 
starch is practically dissolved, then dilute to 1 liter. 

(ec) Porassrum IopipE SoLUTION.—Dissolve 150 g of potassium 
iodide free from iodate in distilled water and dilute to 1,000 cc. 

(f) Hanus SoLurion.—Dissolve 13.2 g of iodine in 1,000 cc of 
99.5 per cent glacial acetic acid, which will not reduce chromic 
acid. Add enough bromine to double the halogen content, 
determined by titration (3 cc of bromine is about the proper 
amount). The iodine may be dissolved by the aid of heat, but 
the solution should be cold when the bromine is added. 

(g) ALCOHOLIC SoprtumM HypRoxIDE SOLUTION.—Dissolve pure 
sodium hydroxide in 95 per cent ethyl alcohol in the proportion 
of about 22 g per 1,000 ce. Let stand in a stoppered bottle. 
Decant the clear liquid into another bottle and keep well stoppered. 
This solution should be colorless or only slightly yellow when used, 
and it will keep colorless longer if the alcohol is previously treated 
with sodium hydroxide (about 80 g to 1,000 cc), kept at about 
50° C. for 15 days, and then distilled. 


WASHINGTON : GOVERNMENT PRINTING OFFICE: 1924 


DEPARTMENT OF COMMERCE. 


BUREAU OF STANDARDS. 


S. W. STRATTON, Director. 


CIRCULAR OF THE BUREAU OF STANDARDS. 


No. 97. 


[3d edition. Issued July 3, 1922.] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
GREEN PAINT, SEMIPASTE AND READY MIXED. 


FEDERAL SPECIFICATIONS BOARD. 
STANDARD SPECIFICATION NO. 15. 


This Specification was officially adopted by the Federal Specifications Board on 
February 3, 1922, for the use of the Departments and Independent Establish- 
ments of the Government in the purchase of materials covered by it. 


CONTENTS. 

Page 
Sanpete Ae Aiea. EAE. Aidt’ BAA lies Dae. Thijs EAA ides I 
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ER eC es Ec ey see os his eT Oe EE TS cE SE Vale £0 5 eek Gee re) 

1. GENERAL. 


The paint contemplated by this specification is a chrome green 
paint, and it may be ordered either in the form of semipaste 
pigment ground in linseed oil or as ready-mixed paint. 

The basis of purchase may be either net weight or volume (231 
cubie inches to the gallon). 

(a) PicMENT.—The pigment in both semipaste and ready- 
mixed paints should be a chrome green containing about 23 per 

109836°—22——1 


2 Circular of the Bureau of Standards 


cent of color (sum of lead chromate and insoluble Prussian blue), 
about 10 per cent of magnesium silicate, aluminum silicate, or 
similar siliceous material, and about 67 per cent of barium sul- 
phate. It should be made by precipitating the color on the 
proper base rather than by mixing the individual materials. It 
must yield on analysis: 


oa 


Maximum.) Minimum, 


Per cent. | Per cent. 
Color (total lead chromate and insoluble Prussian blue)... ............e eee e ese efor eee eee eee 
Material soluble in water, including soluble Prussian blue...................... ie cries tan ees 
Acid-soluble or water-soluble calcium in any form, calculated as CaO........... ORE BH Bee Gcn pce oy he 
Material other than color and barium sulphate,................ cee eee cere eeees mike pL WROKE Ba apy sak eh 
The remainder must be barium sulphate. 


(b) Liguip.—The liquid in semipaste paint shall be entirely 
pure raw or refined linseed oil; in ready-mixed paint it shall 
contain not less than 90 per cent pure raw linseed oil, the balance 
to be combined drier and thinner. The thinner shall be turpen- 
tine, volatile mineral spirits, or a mixture thereof. 

(c) SemipastE.—Semipaste paint shall be made by thoroughly 
grinding the pigment with pure raw or refined linseed oil. 

The semipaste as received and three months thereafter shall be 
not caked in the container and shall break up readily in linseed 
oil to form a smooth paint of brushing consistency. It shall mix 
readily with linseed oil, turpentine, or volatile mineral spirits, or 
any combination of these substances, in all proportions, without 
curdling. The color and hiding power when specified shall be 
equal to that of a sample mutually agreed upon by buyer and 
seller. The weight per gallon shall be not less than 16 pounds. 
The paste shall consist of: 


Maximum.) Minimum. 


Per cent. | Percent. 
72 68 


Bad (550 l-) 0] ee nr Rn aOR GMRaE CEN sa eaMee Hr Wenge og CRM MORTEM UN ISIS yp 
Linseed ol os 08 bos cece ago obaleelbas Cutis Raa ea RN adoie RE. cea Vn ea ee 32 28 
Moisture and.other volatile matters. <..060.. su oc bc osns0.0.0.0.0 0 00 cuen celcen sna avai Li ey J Are reer ae 
Coarse particles and ‘‘skins’”’ (total residue retained on No. 325 screen based on 

PIPMENL) FST Ab aie clon olvl ge sdawleltey Gin sMUstche cachet els coe Aa abe «nhs Wa a:cholele @ aia alitn eee SiS) tT. eens seo 


(d) Reapy-MixED Parnt.—Ready-mixed paint shall be well 
ground, shall not settle badly or cake in the container, shall be 
readily broken up with a paddle to a smooth uniform paint of good 
brushing consistency, and shall dry within 18 hours to a full oil 
gloss, without streaking, running, or sagging. ‘The color and 
hiding power when specified shall be equal to those of a sample 


Specification for Green Paint 3 


mutually agreed upon by buyer and seller. The weight per gallon 
shall be not less than 12 pounds. ‘The paint shall consist of: 


Maximum.) Minimum. 


Percent. | Percent. 
| ee eae a RSS Oe Sele Ne TS SR iy Oe ene eS 55 
Liquid (containing at least 90 per cent linseed oil)................................ 50 45 
Be eaten eo eee EL. es ei ican oath ccs bile eae OSC Boldccde cea gt O28 |pake eto ee 
Coarse particles and “‘skins’’ (total residue retained on No. 325 screen based on 
eR Mr ee eae W HS es ae Gh a Cates. state lls eid ake wie ecd « kk las og held Dc e-s cn'p cena 2i52 | aad See 


NotTe.—Deliveries will, in general, be sampled and tested by the following methods, but the purchaser 
reserves the right to use any additional available information to ascertain whether the material meets 


the specification. 
2. SAMPLING. 


It is mutually agreed by buyer and seller that a single package 
out of each lot of not more than 1000 packages shall be taken 
as representative of the whole. Whenever possible an original 
unopened container shall be sent to the laboratory, and when this 
is for any reason not done, the inspector shall determine by thorough 
testing with a paddle or spatula whether the material meets the 
requirement regarding caking in the container. He shall then 
thoroughly mix the contents of the container and draw a sample 
of not less than 5 pounds. This sample shall be placed in a clean, 
dry metal or glass container, which it must nearly fill. The con- 
tainer shall be closed with a tight cover, sealed, marked, and sent 
to the laboratory for test with the inspector’s report on caking. 

When requested, a duplicate sample may be taken from the 
same package and delivered to the seller, and the inspector may 
take a third sample to hold for test in case of dispute. 


3. LABORATORY EXAMINATION OF SEMIPASTE. 


(a) CAKING IN CONTAINER. — When an original package is 
received in the laboratory it shall be weighed, opened, and stirred 
with a stiff spatula or paddle. The paste must be no more diffi- 
.cult to break up than a normal good grade of semipaste paint. 
The semipaste shall finally be thoroughly mixed, removed from 
the container, and the container wiped clean and weighed. ‘This 
weight subtracted from the weight of the original package gives 
the net weight of the contents. A portion of thoroughly mixed 
semipaste shall be placed in a clean container and the portions 
for the remaining tests promptly weighed out. 

(b) CoLlor.—Place some of the paint on a clean, clear glass 
plate. Place some of the standard agreed upon beside the sample 
on the plate, turn the glass over, and compare the colors. 


4 Circular of the Bureau of Standards 


(c) WEIGHT PER GALLON.—From the weight of a known volume 
of the paste calculate the specific gravity, which multiplied by 
8.33 gives the weight in pounds per gallon. Any suitable con- 
tainer of known volume may be used for the purpose, but a short 
cylinder of heavy glass with rounded bottom about 75 mm high 
and having a capacity of from 125 to 175 cc (a glass cap to keep 
dust from reagent bottle stopper) is a convenient apparatus for 
the purpose. ‘The capacity of this vessel is determined to within 
tcc. The paste is packed into it until completely full, the top 
leveled off smooth with a spatula, and weighed to +0.5 g. Sub- 
tract the weight of the empty container and divide the remainder 
by the number of cubic centimeters representing the capacity of 
the container. ‘he quotient is the specific gravity, which can be 
thus determined within +2 in the second decimal place. 

(d) Mixinc wirH LinsEED O1.—One hundred grams of the 
paste shall be placed in a cup, 30 cc of linseed oil added slowly with 
careful stirring and mixing with a spatula or paddle. ‘The result- 
ing mixture must be smooth and of good brushing consistency. 

(ec) MoIstURE AND OTHER VOLATILE MaTTEeR. — Weigh accu- 
rately from 3 to 5 g of the paste into a tared flat-bottomed dish 
about 5 cm in diameter, spreading the paste over the bottom. 
Heat at 105 to 110° C. for one hour, cool, and weigh. Calculate 
loss in weight as percentage of moisture and volatile matter. 

({) PERCENTAGE OF PiGMENT.—Weigh accurately about 15 g 
of the paste into a weighed centrifuge tube. Add 20 to 30 cc of 
“extraction mixture’’ (see reagents), mix thoroughly with a glass 
rod, wash the rod with more of the extraction mixture, and add 
sufficient of the reagent to make a total of 60 cc in the tube. 
Place the tube in the container of a centrifuge, surround with 
water, and counterbalance the container of the opposite arm 
with a similar tube or a tube with water. Whirl at a moderate 
speed until well settled. Decant the clear supernatant liquid. 
Repeat the extraction twice with 40 cc of extraction mixture and 
once with 40 cc of ether. After drawing off the ether, set the 
tube in a beaker of water at about 80° C. or on top of a warm oven 
for 10 minutes, then in an oven at 110 to 115° C. for two hours. 
Cool, weigh, and calculate the percentage of pigment. Grind 
the pigment to a fine powder, pass through a No. 80 sereen to 
remove any skins, and preserve in a stoppered bottle. 

(g) PREPARATION OF Farry Acips.—To about 25 g of the 
paste in a porcelain casserole, add 15 cc of aqueous sodium 


Specification for Green Paint 5 


hydroxide (see reagents) and 75 cc of ethyl alcohol, mix and 
heat uncovered on a steam bath until saponification is complete — 
(about one hour). Add 100 cc of water, boil, add an excess 
of sulphuric acid of specific gravity 1.2 (8 to 10 cc will usually 
suffice), boil, stir, and transfer to a separatory funnel to which 
some water has been previously added. Draw off as much 
as possible of the acid aqueous layer, wash once with water, 
then add 50 cc of water and 50 cc of ether. Shake very gently 
with a whirling motion to dissolve the fatty acids in the ether, 
but not so violently as to form anemulsion. Draw off the aqueous 
layer and wash the ether layer with one 15 cc portion of water 
and then with 5 cc portions of water until free from sulphuric 
acid. ‘Then draw off the water layer completely. Transfer the 
ether solution to a dry flask and add 25 to 50 g anhydrous sodium 
sulphate. Stopper the flask and let stand with occasional shaking 
at a temperature below 25° C. until the water is completely 
removed from the ether solution, which will be shown by the 
solution becoming perfectly clear above the solid sodium sulphate. 
Decant this clear solution, if necessary, through a dry filter 
paper, into a dry 100 cc Erlenmeyer flask. Pass a rapid current 
of dry air (pass through a CaCl, tower) into the mouth of the 
Erlenmeyer flask and heat to a temperature below 75° C. on a 
dry, hot plate until the ether is entirely driven off. 

2 NoTtE.—It is important to follow all of the details, since ether generally contains 
alcohol and after washing with water always contains water. It is very difficult 
to remove water and alcohol by evaporation from fatty acids, but the washing of the 
ether solution and subsequent drying with anhydrous sodium sulphate removes both 
water and alcohol. Ether, in the absence of water and alcohol, is easily removed 
from fatty acids by gentle heat. 

The fatty acids prepared as above should be kept in a stoppered 
flask and examined at once. 

(h) TEST FOR MINERAL Ol, AND OTHER UNSAPONIFIABLE 
MATTER.—Place 10 drops of the fatty acids (g) in a 50 cc test 
tube, add 5 cc of alcoholic soda (see Reagents), boil vigorously 
for five minutes, add 40 cc of water, and ‘mix; a clear solution 
indicates that not more than traces of unsaponifiable matter are 
present. If the solution is not clear, the oil is not pure linseed oil. 

(2) lopINE NUMBER OF Farry Acips.—Place a small quantity of 
the fatty acids (g) in a small weighing burette or beaker. Weigh 
accurately. Transfer by dropping about 0.15 g (0.10 to 0.20 g) 
into a 500 cc bottle having a well-ground glass stopper, or an 
Erlenmeyer flask having a specially flanged neck for the iodine 

109836°—22—2 


6 Circular of the Bureau of Standards 


test. Reweigh the burette or beaker and determine amount of 
sample used. Add 10 ce of chloroform. Whirl the bottle to 
dissolve the sample. Add 10 cc of chloroform to two empty bot- 
tles like that used for the sample. Add to each bottle 25 ce of 
the Hanus solution (see reagents) and let stand with occasional 
shaking for one-half hour. Add 10 cc of the 15 per cent potas- 
sium iodide solution and 100 cc of water, and titrate with stand- 
ard sodium thiosulphate, using starch as indicator. ‘The titrations 
on the two blank tests should agree within 0.1 cc. From the 
difference between the’ average of the blank titrations and the 
titration on the sample and the iodine value of the thiosulphate 
solution, calculate the iodine number of the sample tested. (Io- 
dine number is centigrams of iodine to 1 g of sample.) If the 
iodine number is less than 170, the oil does not meet the specifica- 
tion. | 

(7) COARSE PARTICLES AND SkiNs.—Dry in an oven at 105 to 
110° C. a No. 325 screen, cool, and weigh accurately. Weigh an 
amount of semipaste containing 10 g of pigment (see 3 (f)), add 
50 ce of kerosene, mix thoroughly, and wash with kerosene 
through the screen, breaking up all lumps but not grinding. After 
washing with kerosene until all but the particles too coarse to pass 
the screen have been washed through, wash all kerosene from the 
screen with ether or petroleum ether, heat the screen for one hour 
at 105 to 110° C., cool, and weigh. 


4. ANALYSIS OF PIGMENT. 


(a) QUALITATIVE ANALYsIS.—Test for Prussian blue by boiling a 
portion of the pigment with sodium hydroxide solution. A yellow 
or yellow-brown precipitate with a yellow liquid above it should 
result. Filter, add a mixture of ferric and fetrous salts to the 
filtrate, and render acid with dilute hydrochloric acid. A blue 
color indicates Prussian blue in the sample. Ignite another por- 
tion very gently to decompose the Prussian blue and make a 
qualitative analysis of the residue. 

(b) MatreR SoLUBLE IN WaATER.—Transfer 2.5 g of the pig- 
ment to a graduated 250 ce flask, add 100 ce of water, boil for 
5 minutes, cool, fill to mark with water, mix, and allow to settle. 
Pour the supernatant liquid through a dry paper and discard the 
first 20 cc. “Then evaporate roo cc of the clear filtrate to dryness 
in a weighed dish, heat for one hour at 105 to 110° C., cool, and 
weigh. ae tee ie 


Specification for Green Patnt 7 


(c) BARTUM SULPHATE AND SILICEOUS MATERIAL.—Heat a 1 ¢ 
portion of the pigment very gently in a small porcelain dish. 
The heat must be so regulated by moving the burner that the 
Prussian blue is thoroughly decomposed without rendering the 
iron difficultly soluble. Allow to cool, transfer to a 400 cc beaker, 
add 20 ce of concentrated hydrochloric acid, heat on steam bath 
for 30 minutes, boil for 5 minutes, dilute with hot water to about 
250 cc, filter on paper while hot, wash thoroughly with hot water 
until the washings are free from lead and chlorine, and ignite and 
weigh the residue, which will be barium sulphate and siliceous 
material. Mix the ignited residue with about ro times its weight 
of anhydrous sodium carbonate (grinding the mixture in an agate 
mortar if necessary), and fuse the mixture in a covered platinum 
crucible, heating about one hour. Let cool, place crucible and 
cover in a 250 cc beaker, add about 100 cc of water, and heat 
until the melt is disintegrated. Filter on paper (leaving crucible 
and cover in beaker) and wash the beaker and filter thoroughly 
with hot water to remove soluble sulphates. Place the beaker 
containing the crucible and cover under the funnel, pierce the 
filter with a glass rod, and wash the carbonate residue into the 
beaker by means of a jet of hot water. Wash the paper with hot, 
dilute hydrochloric acid (1:1), and then with hot water. If the 
earbonate residue is not completely dissolved, add sufficient dilute 
hydrochloric acid to effect solution, and remove crucible and cover, 
washing them with a jet of water. Heat the solution to boiling 
and add 1o to 15 cc of dilute sulphuric acid, and continue the 
boiling for 10 or 15 minutes longer. Let the precipitate settle, 
filter on a weighed Gooch crucible, wash with hot water, ignite, 
cool, and weigh as BaSO,. Subtract from the result of the 
previous determination to obtain the siliceous material. 

(d) LEAD AND CHROMIUM.—Unite the filtrate and washings 
from barium sulphate and siliceous material (see (c)), dilute to 
500 cc, nearly neutralize with ammonium hydroxide, and pass 
in a rapid stream of hydrogen sulphide until all the lead is pre- 
cipitated as Pb§; filter, wash with water containing a little hydro- 
gen sulphide, dissolve in hot nitric acid (1:3), and determine lead 
as sulphate in usual manner, weighing as PbSO,. Boil the fil- 
trate from the lead sulphide to expel hydrogen sulphide. Add 
sodium peroxide in sufficient amount to render the solution alka- 
line and to oxidize the chromium to chromate. Boil until the 
hydrogen peroxide is driven off, cool, acidify with sulphuric acid 


8 Circular of the Bureau of Standards 


(1:4), add a measured excess of a freshly prepared solution of 
ferrous sulphate, and titrate the excess of ferrous iron with stand- 
ard potassium dichromate, using potassium ferricyanide solution 
as outside indicator. ‘Titrate a blank of an equal volume of the 
ferrous sulphate solution with the standard potassium dichromate. 
From the difference between the titration on the blank and on 
the sample, calculate the chromium in the sample to PbCrQ,. 
From the PbCrO, found, calculate the equivalent of PbSO, by 
multiplying by the factor 0.938. Subtract this value from the 
total PbSO, found above and report the remainder as lead com- 
pounds other than chromate, calculated as PbSQ,,. 

(ec) CaLcrum.—Ignite 2 g of the pigment and primaries the 
residue in hydrochloric acid as in 4(c). Then, without filtering 
from the insoluble matter, transfer to a 500 cc volumetric flask, 
saturate with hydrogen sulphide, make alkaline with ammonia, 
fill to the mark, mix, and filter through a dry paper, discarding 
the first 20 cc. ‘Then determine the calcium in 250 cc of the 
filtrate (corresponding to 1 g pigment) by precipitation as oxalate 
and weighing as calcium oxide. 

(f) Cotor.—Add the percentages of matter soluble in water 
4(b), barium sulphate and siliceous material 4(c), lead compounds 
other than chromate calculated as PbSO, 4(d), and calcium oxide 
4(e) and subtract the sum from 100, Call the difference the 
percentage of color. 


5. LABORATORY EXAMINATION OF MIXED PAINT. 


(a) CAKING IN CONTAINER.—Follow the procedure outlined in 
3(a), noting that the paint should be no more difficult to break up 
than a good grade of mixed paint. 

(b) CoLor.—Follow the procedure outlined in 3(0). 

(c) WEIGHT PER GALLON.—Weigh a clean, dry, 100 cc gradu- 
ated flask. Fill to the mark with the thoroughly mixed paint and 
weigh again. ‘The increase in weight expressed in grams, divided 
by 100, gives the specific gravity, which multiplied by 8.33 gives 
the weight in pounds per gallon. 

(d) BRUSHING PROPERTIES AND TIME OF DRYING. —Brush the 
well-mixed paint on a suitable panel, which may be ground glass, 
steel, or well-filled wood. Note whether the paint works satis- 
factorily under the brush. Place the panel in a vertical position 
in a well-ventilated room and let stand for 18 hours. The paint 
should be dry and free from streaks. 


Specification for Green Paint 9 


(ec) WATER.—Mix 100 g of the paint in a 300 ce flask with 75 cc 
of toluol. Connect with a condenser and distill until about 50 cc 
of distillate has been collected in a graduate. ‘The temperature in 
the flask should be then about 105° to 110°C. The number of 
cubic centimeters of water collecting under the toluol in the re- 
ceiver is the percentage of water in the paint. 

({) VOLATILE THINNER.—Follow the procedure outlined in 
3(e). Correct the result for any water found (see 5(e)) and report 
the remainder as volatile thinner. 

(g) PERCENTAGE OF PiGMENT.—Follow the procedure outlined 
in 3(/). 

(h) TESTING NONVOLATILE VEHICLE.—Follow the procedure 
outlined in 3(9), 3(2), and 3(z), except that in the preparation of 
the fatty acids the mixture of paint and alkali is heated on the 
steam bath until all volatile thinner is driven off. 

(2) COARSE PaRTICLES AND Skins.—Follow the procedure out- 
lined in 3(,). | 

(j) TEsTING PicmMENT.—Follow the procedure outlined in 4(a) 
to 4(e), inclusive. 

6. REAGENTS. 


(a) EXTRACTION MIxTURE.— 
5 volumes benzol. 
4 volumes methyl alcohol 
1 volume acetone. 

(6) AQuEOUS Sopium HypRoxIpE.—Dissolve 100 g of sodium 
hydroxide in distilled water and dilute to 300 cc. 

(c) STANDARD SODIUM THIOSULPHATE SOLUTION.—Dissolve pure 
sodium thiosulphate in distilled water (that has been well boiled 
to free it from carbon dioxide) in the proportion of 24.83. g crys- 
tallized sodium thiosulphate to 1,000 cc of the solution. It is 
best to let this solution stand for about two weeks before stan- 
dardizing. Standardize with pure resublimed iodine. (See Tread- 
well-Hall, Analytical Chemistry, vol. 2, 3d ed., p. 646.) This so- 
lution will be approximately decinormal, and it is best to leave 
it as it is after determining its exact iodine value, rather than to 
attempt to adjust it to exactly decinormal. Preserve in a stock 
bottle provided with a guard tube filled with soda lime. 

(dq) STaRcH SOLUTION.—Stir up to 2 to 3 g of potato starch or 
5 g of soluble starch with 100 cc of 1 per cent salicylic acid solu- 


IO Circular of the Bureau of Standards 


tion, add 300 to 400 ce boiling water, and boil the mixture until 
the starch is practically dissolved, then dilute to 1 liter. 

(ec) Porassrtum IopIDE SoLutTIoN.—Dissolve 150 g of potassium 
iodide free from iodate in distilled water and dilute to 1,000 cc. 

(f) Hanus SoLution.—Dissolve 13.2 g of iodine in 1,000 cc 
of 99.5 per cent glacial acetic acid, which will not reduce chromic 
acid. Add enough bromine to double the halogen content, deter- 
mined by titration (3 cc of bromine is about the proper amount). 
The iodine may be dissolved by the aid of heat, but the solution 
should be cold when the bromine is added. 

(g) ALcoHOLIC SoprumM HypROxIDE SOLUTION.—Dissolve pure 
sodium hydroxide in 95 per cent ethyl alcohol in the proportion 
of about 22 g per 1,000cc. Let stand in a stoppered bottle. 
Decant the clear liquid into another bottle and keep well stop- 
pered. This solution should be colorless or only slightly yellow 
when used, and it will keep colorless longer if the alcohol is pre- 
viously treated with sodium hydroxide (about 80 g to 1,000 cc), 
kept at about 50° C. for 15 days, and then distilled. 

(h) STANDARD FERROUS SULPHATE SOLUTION.—Dissolve 14 g of 
pure crystallized ferrous sulphate (FeSO, 7H,O) in about 500 cc 
of water, to which 25 cc of concentrated H,SO, has been added, 
and then dilute to 1,000 cc. This solution should be freshly 
standardized when needed, as it does not keep well. 

(1) STANDARD POTASSIUM DICHROMATE SOLUTION.—Dissolve 
4.903 g of pure dry crystallized potassium dichromate in water 
and dilute to 1,000 cc. One cubic centimeter of this solution 
corresponds to 0.0108 g PbCrO,, or o.oror g PbSO,. 

(j) PoTasstuM FERRICYANIDE SOLUTION.—Dissolve a piece half 
as big as a small pea in 50 cc of water. This solution must be 
made fresh when wanted, because it does not keep. 


‘Samaaaspinouepupaapinsae-nadagemaaaapaaaoiae neaeeegineueondamaesoee pane aera nena neen eee eee 
ADDITIONAL COPIES 
OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 
AT 
5 CENTS PER COPY 


V 


WASHINGTON : GOVERNMENT PRINTING OFFICE : 1922 


“ 


DEPARTMENT OF COMMERCE. 
BUREAU OF STANDARDS. 


CIRCULAR OF THE BUREAU OF STANDARDS. 
No. 98. 


[Second edition. Issued February 28, 1923.] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
VOLATILE MINERAL SPIRITS FOR THINNING PAINTS.! 


SnEEnEEiEeiieeaet 


FEDERAL SPECIFICATIONS BOARD. 


STANDARD SPECIFICATION No. 16. 
[Revised January 2, 1923.j 
This specification was officially adopted by the Federal Specifications Board 
on February 3, 1922, for the use of the departments and independent establish- 
ments of the Government in the purchase of volatile mineral spirits for thin- 
ning paints. 


CONTENTS. 

Page. 
oS co Boi it ie di eet Allain Sap ‘Saad. Bre nara aoa doll Ai tiaities ysy I 
a. Detection and removal of separated water.i).. 0.6.0.0. 0 cece ccc 2 
te da ile, 29s. <> sak ee eek: -Liaaters «dry dpbeterehs die. db ae 2 
Uae MR ITIACION 6 oa se. ge oss ates o 8 Sie Wonk Lat ale ese Bock Cee 3 
Si og Uh cae ey pane ee a aE Ne rae Waray Mae Bac Pen’ © ART ania A Fo 9 

1. GENERAL. 


This specification applies only to petroleum distillates, known 
as mineral spirits. The material delivered under this specifica- 
tion shall conform to the following requirements: 

APPEARANCE.— hall be clear and free from suspended matter 
and water. 

CoLor.—Shall be no darker than an aqueous solution of potas- 
sium dichromate containing 0.0048 g per liter (this corresponds to 
No. 21 Saybolt chromometer). 

Spot TEst.—Shall evaporate completely from filter paper. 


Petroleum Products, Bureau of Mines Technical Paper 323. 
27818°—23 ‘ 


2 Circular of the Bureau of Standards. 


FLasH Pornt.—Shall be not lower than 30° C. (86° F.) when 
tested in a closed cup tester. 

BLACKENING.—Shall not blacken clean metallic copper. Distil- 
late below 130° C. (266° F.) shall not exceed 5 percent. Distillate 
below 230° C. (446° F.) shall be not less than 97 per cent. 

Acipity.—shall be neutral. 


2. DETECTION AND REMOVAL OF SEPARATED WATER. 


Draw a portion by means of a glass or metal container with a 
removable stopper or top, or with a ‘‘thief,’’ from the lowest part 
of the container, or by opening the bottom valve of the perfectly 
level tank car. If water is found to be present, draw it all out, 
record the quantity, and deduct it from the total volume of liquid 
delivered. 

NorTrE.—Deliveries will in general be sampled and tested by the following methods, 


but the purchaser reserves the right to use any additional available information to 
ascertain whether the material meets the specification. 


3. SAMPLING. 


The method of sampling given under (a) should be used when- 
ever feasible. When method (a) is not applicable, method (0), 
(c), or (d) is to be used, according to the special conditions that 
obtain. , 

(2) WuiILe LoapInc TANK Car OR WHILE FILLING CONTAINERS 
FOR SHIPMENT.—Samples shall be drawn by the purchaser’s 
imspector at the discharge pipe where it enters the receiving 
vessel or vessels. The composite sample shall be not less than 5 
gallons and shall consist of small portions of not more than 1 
quart each taken at regular intervals during the entire period of 
loading or filling. The composite sample thus obtained shall be 
thoroughly mixed, and from it three samples of not less than 1 
quart each shall be placed in clean, dry glass bottles or tin cans, 
which must be nearly filled with the sample and securely stoppered 
with new clean corks or well-fitting covers or caps. These shall 
be sealed and distinctly labeled by the inspector. One shall be 
delivered to the buyer, one to the seller, and the third held for 
check in case of dispute. 

(6) From LoapEp TANK CAR OR OTHER LARGE VESSEL.—The 
composite sample taken shall be not less than 5 gallons and shall 
consist of numerous small samples of not more than 1 quart each 
taken from the top, bottom, and intermediate points by means 
of a metal or glass container with removable stopper or top. — 


Specification for Mineral Spirtts. 3 


This device attached to a suitable pole is lowered to the various 
desired depths, when the stopper or top is removed and the con- 
tainer allowed to fill. The sample thus obtained is handled as 
in (a). : 

(c) BARRELS AND Drums.—Barrels and drums shall be sampled 
after gauging contents. Five per cent of the packages in any 
shipment or delivery shall be represented in the sample. Thor- 
oughly mix the contents of each barrel to be sampled by stirring 
with a clean rod and withdraw a portion from about the center 
by means of a “thief” or other sampling device. The com- 
posite sample thus obtained shall be not less than 3 quarts, shall 
consist of equal portions of not less than one-half pint from each 
package sampled, and shall be handled as in (a). Should the 
inspector suspect adulteration, he shall draw the samples from 
the suspected packages. 

(d) SMALL CONTAINERS, CANS, ETC., OF 10 GALLONS OR LESS.— 
These should be sampled, while filling, by method (a) whenever 
possible; but in case this is impossible, the composite sample 
taken shall be not less than 3 quarts. This shall be drawn from 
at least five packages (from all when fewer), and in no case from 
less than 2 per cent of the packages. The composite sample 
thus taken shall be thoroughly mixed and subdivided as in (a). 


é. 4. LABORATORY EXAMINATION. 


(a) APPEARANCE.—Exaimine to determine compliance with the 
specification. 

(6) CoLor.—Compare in any suitable apparatus the depth of 
color of the sample with the depth of color of a fresh solution of 
potassium dichromate in distilled water containing 0.0048 g K,Cr,0, 
per liter. (If desired, the color may be determined in a Saybolt 
chromometer, in which case the color must be no darker than 
No. 21 on that scale.) 

(c) Spor TEest.—Transfer five drops of the mineral spirits by 
means of a small pipette or burette to the center of a clean white 
filter paper supported on a 7-cm crystallizing dish and allow the 
liquid to evaporate at room temperature, away from direct sun- 
light. There should be no oily spot left after 30 minutes. 

(qd) FLAsH Point.—Determine with either the ‘‘Tag”’ or Elliott 
closed-cup tester. The former is preferred.’ 


2 Directions for using the ‘‘Tag”’ tester may be found in A. S. T. M. Standards Ds6-21 and in Bureau 
of Mines Technical Paper No. 323. Directionsfor using the Elliott cup may be found in Proceedings 
A.S. T. M., 1917, pt. 1, p. 414. 


4 Circular of the Bureau of Standards. 


(ec) BLACKENING.—Place a clean strip of mechanically polished 
pure sheet copper, about }4 inch wide and 3 inches long (1.3 cm 
by 7.5 cm) in a glass test tube about 34 inch wide and 18 inches 
long (1.9 by 46 cm). Add sufficient of the sample to be tested 
to completely cover the strip and heat rapidly to its boiling point 
(it is most convenient to heat the tube by immersion in an oil 
bath maintained at a temperature slightly higher than the initial 
boiling point of the mineral spirits). Keep the sample at its 
boiling point, without any actual distillation taking place, for 30 
minutes and then examine the copper strip for blackening. A 
slight tarnish shall be disregarded, but any marked blackening 
shall be cause for rejection. | 

(f) DistILLATION.—Use the A. S. T. M. (D 86-21 T) method 
as described below, except that it will be necessary to read the 
volume of the distillate at 130° C. and at 230° C. and the distilla- 
tion need not be carried beyond the 230° C. (446° F.) point. 


APPARATUS. 


Flask.—The standard 100 cc Engler flask is shown in Figure 1, 
the dimensions and allowable tolerance being as follows: 


Dimensions of Engler flask. 


. @f- 
Description. he wpe 4 . Inches. ei 
Diancter of bulb; outside <9 see evo had ane Pee ck cals rie 6.5 2. 56 0.2 
Diameter of neck, insides... 2e. op oh i oie ae Sk me he oe Bal ee een cee al 1.6 - 63 el 
Lenvth of meek ke castes ss poe becca sees coe Geert es re cee eee 15.0 5.91 4 
Length of vapor tab@y 20) os jccols wire ds ue o bcs maf pts Sone elas oe oie ee aS ee 10. 0 3.94 .3 
Diameter of vapor fube, outside. sco aac te est se pes nee -6 24 .05 
Diameter of vapor tuhe, inside. . 5..5....509 <b e sas ab cen ie wy oe ee .4 .16 05 
Thickness of vapor tube walle... 3. As G6 a et ee ee oe ns ee eee lt . 04 .05 


The position of the vapor tube shall be 9 cm (3.55 inches) 
+3 mm above the surface of the liquid when the flask contains 
its charge of 100 cc.. The tube is approximately in the middle 
of the neck and set at an angle of 75° (tolerance +3°) with the 
vertical. vee 

Condenser.—The condenser (Fig. 2) consists of a 9/16 inch 
OD No. 20 Stubbs gauge seamless brass tube 22 inches long. 
It is set at an angle of 75° from the perpendicular and is 
surrounded with a cooling bath 15 inches long, approximately 
4 inches wide by 6 inches high. ‘The lower end of the condenser 
tube is cut off at an acute angle and curved downward for a length 
of 3 inches and slightly backward, so as to insure contact with 


Specification for Mineral Spirits. 5 


the wall of the graduate at a point 1 to 11/ inches below the top 
of the graduate when it is in position to receive the distillate. 
Shield.—The shield (Fig. 2) is made of approximately 22- 
gauge sheet metal and is 19 inches high, 11 inches long, and 8 inches 
wide, with a door on one narrow side, with two openings, 1 inch in 


x 

z & 

Ro 

gS 

£% o Pag eae 
ie 
S98 
ry 
8. LAS 5 [oe ie a Level of liguid surface whan 


Hask confains 100 CC 


————— eS = 
620M 
Outside 


Fic. 1.—Standard 100 cc Engler flask for use in making distillation tests. 


diameter, equally spaced, in each of the two narrow sides, and 
with a slot cut in one side for the vapor tube. The centers of these 
four openings are 814 inches below the top of the shield. There are 
also three 14-inch holes in each of the four sides, with their centers 
1 inch above the base of the shield. 

Ring support and hard asbestos boards.—The ring support is of 
the ordinary laboratory type, 4 inches or larger in diameter, and is 

27818 °—23——_2 


6 Circular of the Bureau of Standards. 


supported on a stand inside the shield. There are two hard 
asbestos boards, one 6 by 6 by % inch, with a hole 1}4 inches in 
diameter in its center, the sides of which shall be perpendicular to 
the surface; the other, an asbestos board to fit tightly inside the 
shield, with an opening 4 inches in diameter concentric with the 
ring support. ‘These are arranged as follows: The second asbestos 
board is placed on the ring and the first or smaller asbestos board 
on top, so that it may be moved in accordance with the directions 
for placing the distilling flask. Direct heat is applied to the flask 
only through the 1 14-inch opening in the first asbestos board. 


errr 


Ice Water Bath 


2 "Outside Diameter 
—_~~~_ No. 20 Gage Seamless 


7, 


: Blotting 
~ Paper 


Tp 


Fic. 2.—Distillation outfit (A. S. T. M.) arvanged for use of gas burner. 


Gas burner or electric heater—Gas burner: The burner is so 
constructed that sufficient heat can be obtained to distill the 
product at the uniform rate specified below. The flame should 
never be so large that it spreads over a circle of diameter greater 
than 314 inches on the under surface of the asbestos board. A sen- 
sitive regulating valve is a necessary adjunct, as it gives complete 
control of heating. 

Electric heater: The electric heater, which may be used in 
place of the gas flame, shall be capable of bringing over the first 
drop within the time specified below when started cold and of con- 
tinuing the distillation at the uniform rate. ‘The electric heater 


Specification for Mineral Spirits. 7 


shall be fitted with an asbestos board top 1% to 1% inch thick, having 
a hole 11% inches in diameter in the center. When an electric 
heater is employed, the portion of the shield above the asbestos 
board shall be the same as with the gas burner, but the part below 
may be omitted. | 

Thermometer.—A. S. T. M. high-distillation thermometer shall 
conform to the following specifications: 

Type: Etched stem glass. 

Total length: 381 mm. 

Stem: Plain front, enamel back, suitable thermometer tubing; diameter, 6 to 7 mm. 

Bulb: Corning normal, Jena 16 III, or equally suitable thermometric glass; length, 
1o to 15 mm; diameter, 5 to 6 mm. 

Actuating liquid: Mercury. 

Range: 30 to 760° F., or o to 400° C. 

Immersion: Total. : 

Distance to 30° F., or 0° C. mark from bottom of bulb: 25 to 35 mm. 

Distance to 760° F.., or 400° C. mark from top of tube: 30 to 45 mm. 

Filled: Nitrogen gas. 

Top finish: Glass ring. 

Graduation: All lines, figures, and letters clear cut and distinct; scale graduated 
in 2° F. or 1° C. divisions and numbered every 20° F. or 10° C., the first and each 
succeeding 10° F. (5° C.) to be longer than the others. 

Special markings: A. S. T. M. High Distillation, serial number, and manufacturer’s 
name or trade-mark etched on the stem. 

Accuracy: Error at any point on scale shall not exceed one smallest scale division 
up to 700° F. or 370° C. 

Tests for permanency of range: After being subjected to a temperature of 700° F. 
or 370° C. for 24 hours the accuracy shall be within the limit specified. 

Points to be tested for certification: 32°, 212°, 400°, 700° F. or 0°, 100°, 200°, 370° C. 


Graduate.—The graduate shall be of the cylindrical type, of 
uniform diameter, with a pressed or molded base and a lipped 
top. The cylinder shall be graduated to contain roo cc and the 
graduated portion shall be not less than 7 inches nor more than 
8 inches long. It shall be graduated in single cubic centimeters, 
and each fifth mark shall be distinguished by alonger line. It shall 
be numbered from the bottom up at intervals of ro ce. The dis- 
tance from the roo cc mark to the rim shall be not less than 114 
inches nor more than 134 inches. ‘The graduations shall not be 
in error by more than 1 cc at any point on the scale. 


PROCEDURE. 


The condenser bath shall be filled with cracked ice* and 
enough water added to cover the condenser tube. The tempera- 
ture shall be maintained between 32 and 40° F. (o and 4.5° C.). 


% Any other convenient cooling medium may be used. 


8 Circular of the Bureau of Standards. 


The condenser tube shall be swabbed to remove any liquid 
remaining from the previous test. A piece of soft cloth attached 
to a cord or copper wire may be used for this purpose. 

The bulb of the distillation thermometer shall be covered 
uniformly with a long-fiber absorbent cotton weighing not less 
than 3 nor more than 5 mg. A fresh portion of clean cotton shall 
be used for each distillation. 

One hundred cubic centimeters of the product shall be meas- 
ured in the roo ce graduated cylinder at 55 to 65° F. (12.8 to 
18.3° C.) and transferred directly to the Engler flask. None of 
the liquid shall be permitted to flow into the vapor tube. 

The thermometer provided with a cork shall be fitted tightly 
into the flask; so that it will be in the middle of the neck and so 
that the lower end of the capillary tube is on a level with the 
inside of the bottom of the vapor outlet tube at its junction with 
the neck of the flask. 

The charged flask shall be placed in the 14-inch opening 
in the 6 by 6 inch asbestos board, with the vapor outlet tube 
inserted into the condenser tube. A tight connection may be 
made by means of a cork through which the vapor tube passes. 
The position of the flask shall be so adjusted that the vapor tube 
extends into the condenser tube not less than 1 inch nor more than 
2 inches. 

The graduated cylinder used in measuring the charge shall be 
placed, without drying, at the outlet of the condenser tube in 
such a position that the condenser tube shall extend into the 
graduate at least 1 inch but not below the 100 cc mark. Unless 
the temperature is between 55 and 65° F. (12.8 and 18.3° C.) the 
receiving graduate shall be immersed up to the 100 ce mark in a 
transparent bath maintained between these temperatures. The 
top of the graduate shall be covered closely during the distillation 
with a piece of blotting paper or its equivalent cut so as to fit the 
condenser tube tightly. 

When everything is in readiness, heat shall be applied at a 
uniform rate, so regulated that the first drop of condensate falls 
from the condenser in not less than 5 nor more than io minutes. 
When the first drop falls from the end of the condenser, the — 
reading of the distillation thermometer shall be recorded as the 
wmitial boiling point. ‘The receiving cylinder shall then be moved 
so that the end of the condenser tube shall touch the side of the 
cylinder. The heat shall then be so regulated that the distilla- 
tion will proceed at a uniform rate of not less than 4 nor more 


Specification for Mineral Spirits. 9 


than 5 cc per minute. The reading of the distillation thermometer 
shall be recorded when the level of the distillate reaches each 
10 cc mark on the graduate. After the 90 per cent point has 
been recorded, the heat may be increased because of the presence 
of the heavy ends which have high boiling points. However, no 
further increase of heat should be applied after this adjustment. 
The 4 to 5 cc rate can rarely be maintained from the 90 per cent 
point to the end of the distillation, but in no case should the 
period between the 90 per cent and the end point be more than 
five minutes. 

The heating shall be continued until the mercury reaches a maxi- 
mum and starts to fall consistently. The highest temperature 
observed on the distillation thermometer shall be recorded as the 
maximum temperature or end point. Usually this point will be 
reached after the bottom of the flask has become dry. ‘The 
total volume of the distillate collected in the receiving graduate 
shall be recorded as the recovery. The cooled residue shall be 
poured from the flask into a small cylinder graduated in 0.1 cc, 
measured when cool and the volume recorded as residue. The 
difference between 100 cc and the sum of the recovery and the 
residue shall be calculated and recorded as distillation loss. 

(g) Acipiry.—Collect in a test tube the cooled residue from 
the distillation flask (see (f)), add three volumes of distilled: water 
and shake the tube thoroughly. Allow the mixture to separate 
and remove the aqueous layer to a clean test tube by means of a 
pipette. Add one drop of a 1 per cent solution of methyl orange. 
No pink or red color should be formed. 


5. BASIS OF PURCHASE. 


(a) Unit.—Mineral spirits shall be purchased either (1) by 
volume, the unit being a gallon of 231 cubic inches at 15.5° C. 
(60° F.), or (2) by weight. A gallon of mineral spirits at 15.5° C. 
(60° F.) weighs 6.3 to 6.8 pounds. The exact weight in pounds 
per gallon of any sample can be determined by multiplying the 
specific gravity at 15.5/15.5° C. (60/60° F.) by 8.33. Example— 
If the specific gravity at 15.5° C. is 0.7642, the weight per gallon 
at this temperature will be 0.7642 X8.33 =6.366 pounds. When 
purchased by weight, quotations shall be by the pound or by 
the 100 pounds. The request for bids will state whether quota- 
tions shall be by the gallon, pound, or 100 pounds. 

(b) CoRRECTION OF VoLUME.—The gallonage paid for shall be 
the volume corrected to a standard temperature of 15.5° C. 


IO Circular of the Bureau of Standards. 


(60° F.). The correction shall be made by deducting from (when 
the temperature of gauging is above 15.5° C.) or adding to (when 
the temperature of gauging is below 15.5° C.) the gallonage as 
gauged. Such deduction or addition shall be computed on the 
basis of a coefficient of expansion of 0.000945 per degree centigrade 
(or 0.000525 per degree Fahrenheit). Example—If the tem- 
perature at which the spirits is gauged is 75° F., and the 
volume delivered (at that temperature) is 8,000 gallons, then 
0.000525 X15 X 8,000 equals the quantity in gallons which must 
be subtracted from 8,000 gallons to give the true gallonage at 
60° F., or, if the temperature at which the spirits is gauged is 
10° C., then 0.000945 X 5.5 X 8,000 equals the quantity in gallons 
which must be added to the gauged volume of 8,000 gallons to 
give the true gallonage at 15.5° C. | 
(c) CERTIFICATION.—Mineral spirits delivered in barrels, drums, 
or tank cars shall either be accompanied by an official gauger’s 
certificate showing the net contents of each container and also 
the temperature of contents at the time of gauging or shall be 
subject to gauging by the purchaser’s inspector. {n the absence 
of a statement of the temperature at the time of gauging on the 
official gauger’s certificate, or in case the barrels show evidence 
of loss by leakage or other shortage, the delivery shall be subject 
to reinspection and regauging by the purchaser’s inspector. 
WASHINGTON, January 2, 1923. 


ADDITIONAL COPIES 
OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 
AT 


5 CENTS PER COPY 


PURCHASER AGREES NOT TO RESELL OR DISTRIBUTE THIS 
COPY FOR PROFIT.—PUB. RES. 57, APPROVED MAY 11, 1922 


V 


oe ee 
te y 


DEPARTMENT OF COMMERCE 


BUREAU OF STANDARDS 


S. W. STRATTON, Director 


CIRCULAR OF THE BUREAU OF STANDARDS 
No. 102 


[2d edition. Issued September 22, 1922] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
COMPOSITE VEHICLE FOR THINNING SEMIPASTE 
PAINTS WHEN THE USE OF STRAIGHT LINSEED OIL 
IS NOT JUSTIFIED 


FEDERAL SPECIFICATIONS BOARD 
STANDARD SPECIFICATION NO. 17 
This specification was officially adopted by the Federal Specifications Board, 


on February 3, 1922, for the use of the Departments and Independent Establish- 
ments of the Government in the purchase of materials covered by it. 


CONTENTS 

Page 
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SE NTE TIES ate eg re cee re wR ahaa eke PEE pO OWE ATTEN is Ca Ope aes OY PRE EES 5 

1. GENERAL 


This specification covers a composite thinner which contains 
in one liquid drying oil, drier, and volatile thinner. Such prep- 
arations are sometimes called ‘“‘ Thinning Mixtures for Paint,” and 
are also offered under a variety of trade names, such as “ Japan 
Oil,” ‘Paint Oil,’ ‘Linseed Oil Substitute,’ etc. The last name 
should, however, not be used, for while such materials may have 
decided merit they are not substitutes for linseed oil. 

The composite thinner must meet the following requirements: 

APPEARANCE.—Shall be clear and free from suspended matter 


and sediment. 
7787°—22 


a 


2 Circular of the Bureau of Standards 


Cotor.—No darker than a solution of 6 g of potassium dichro- 
mate in 100 cc pure sulphuric acid of specific gravity 1.84. 

Opor.—Not offensive, either in bulk or in its subsequent use in 
paint mixtures. 

MrIxING witH LINSEED O1L.—When mixed in any proportion 
with pure raw linseed oil meeting the specifications of B. 5. Cir- 
cular 82, the resulting mixture shall be clear and shall show no 
separation or precipitation on standing 18 hours. 

Drvyinc.—When flowed on glass, the composite thinner shall 
set to touch in not more than 4 hours and dry hard in not more 
than 6 hours. When mixed with an equal volume of pure raw 
linseed oil, the resulting mixture when flowed on glass shall set 
to touch in not more than 6 hours and dry hard in not more than 
8 hours. | 

TOUGHNESS.—The film on glass after baking for 6 hours at 
105 to 110° C (221 to 230° F) shall be glossy, tough, and elastic. 

NonvoLATILE Marrer.—Not less than 50 per cent by weight. 

Acip Numser.—Not more than 12, calculated to basis of non- 
volatile matter. , 

NovtE.—Deliveries will, in general, be sampled and tested by the following methods, 


but the purchaser reserves the right to use any additional available information to 
ascertain whether the material meets the specification. 


2. SAMPLING 


It is mutually agreed by buyer and seller that a single package 
out of each lot of not more than 1000 packages be taken as rep- 
resentative of the whole. Whenever possible an original un- 
opened container shall be sent to the laboratory, and when for any 
reason this is not done, the inspector shall thoroughly mix the 
contents of the containers sampled, transfer not less than 1 quart 
to a clean, dry, glass bottle or tin can, which must be nearly filled 


_ with the sample, securely stoppered with a new, clean cork or well- 


fitting cover or cap, sealed, and distinctly labeled by the in- 
spector. The inspector should take a duplicate from the container 
sampled to hold for check in case of dispute, and when requested 
should take a sample for the seller. 


3. LABORATORY EXAMINATION 


(a2) APPEARANCE.—Fill two test tubes of the same size (15 
cm or 6 inches), with the thoroughly mixed sample to ‘within 
2.5 cm (1 inch) of the top. Stopper the tubes with clean corks. 
Let stand for 24 hours. Note whether sediment is evident in 


Specification for Composite Vehicle 3 


the tubes; if not, shake one tube vigorously and compare the 
two tubes. If they still look alike and the liquid appears clear, 
the sample is considered free from sediment and suspended 
matter. 

(b) CoLor.—Prepare a standard color solution by dissolving 
6 g of pure powdered potassium dichromate in 100 cc of pure 
concentrated sulphuric acid of specific gravity 1.84. Gentle 
heat may be used if necessary to perfect the solution of the dichro- 
mate. The standard color solution and a sample of composite 
thinner to be tested shall be placed in clear, thin-walled’ glass 
tubes of the same diameter. The color comparison shall be made 
by placing the tubes close together and looking through them by 
transmitted light. The tubes used for this test should be 1.5 
to 2.0 cm (5% to 43 inch) in diameter and shall be filled to a depth 
of at least 2.5 cm ( inch). 

(Since the potassium dichromate-sulphuric acid must be freshly 
made for this color comparison, it is frequently more convenient 
to compare samples with a permanently sealed tube of composite 
thinner which has previously been found to be slightly lighter in 
color than the standard solution of 6 g dichromate in sulphuric 
acid. When samples are found to be darker than this sealed tube 
of composite thinner, the dichromate standard should be made up 
for final decision.) 

(c) Opor.—Note the odor of the material in bulk, pour a small 
portion in a shallow flat-bottomed dish, and allow to stand ex- 
posed to the air for not less than 48 hours. Flow some on a glass 
plate and allow to dry in a vertical position for not less than 48 
hours. Note the odor of these test portions from time to time. 
A mild odor of wood turpentine or of fish oil should not be cause 
for rejection, but a pronounced offensive odor, either due to very 
crude wood turpentine, rank fish oil, or other offensive substances, 
would be cause for rejection. 

(d) Mrxine wity LINSEED O1L.—Thoroughly mix 25 cc of the 
sample with 25 cc pure raw linseed oil and transfer portions of the 
mixture to two similar test tubes which shall be filled to within 
2.5 cm (i inch) of the top and stoppered with clean corks. 

Thoroughly mix 5 cc of the sample with 45 cc of pure raw lin- 
seed oil and transfer portions of the mixture to two similar test 
tubes, which shall be filled to within 2.5 cm (1 inch) of the top and 
stoppered with clean corks. 

Let the four tubes stand for 24 hours and note if any sediment 
or curdling is apparent in any of the tubes. If not, shake one tube 


4 Circular of the Bureau of Standards 


of each pair vigorously and then compare with the unshaken tube 
of the same dilution. If the tubes of the same dilution still look 
alike, the sample is considered to mix properly with linseed oil. 

(ce) Dryinc.—Pour the undiluted sample and the mixture with 
an equal volume of linseed oil on clean glass plates not less than 
15 cm (6 inches) long and 10 cm (4 inches) wide. Place the plates 
in a nearly vertical position in a well-ventilated room but not in 
the direct rays of the sun. The temperature of the room should 
be from 21 to 32° C (70 to 90° F). The films are tested at points 
not less than 2.5 cm (1 inch) from the edges of the films by touch- 
ing with the finger. The material is considered to have set to 
touch when gentle pressure of the finger shows a tacky condition 
but none of the material adheres to the finger. The material is 
considered to have dried hard when the pressure that can be ex- 
erted between the thumb and finger does not move the film nor 
leave a mark that remains noticeable after the spot is lightly 
polished. 

(f) ToucHNEss.—Pour the undiluted sample on a clean glass 
plate. Let drain in a vertical position for 2 minutes, then place 
in a horizontal position, film up, and let stand at room tempera- 
ture for 2 hours. Then bake at a temperature of 105 to 110° C 
(221 to 230° F) for 6 hours. Remove from the oven and let stand 
at room temperature for not less than 18 hours. The resulting 
film shall be glossy and when tested with a knife blade shall show 
elastic properties, turning up with the blade of the knife in an 
elastic ribbon without cracking or breaking. The film shall also 
stand rapid light rubbing without breaking the surface. 

(g) NoNVoLATILE Marrer.—Place a portion of the sample in 
a stoppered bottle or weighing pipette. Weigh the container and 
sample. Transfer about 1.5 g of the sample to a weighed flat- 
bottomed metal dish about 8 cm in diameter (a friction-top can 
plug). Weigh the container again and by difference calculate 
the exact weight of the portion of sample transferred to the 
weighed dish. Heat the dish and contents in an oven maintained 
at 105 to 110° C (221 to 230° F) for 3 hours. Cool and weigh. 
From the weight of the residue left in the dish and weight of the 
sample taken calculate the percentage of nonvolatile matter. 

(h) Actp NumBer.—Place a portion of the sample in a stop- 
pered bottle or weighing pipette. Weigh the container and 
sample. Transfer an amount corresponding to between 1 and 2 g 
of nonvolatile matter (see (g)) to a 200 cc Erlenmeyer flask, 
reweigh the container and calculate the exact weight taken, add 


Specification for Composite Vehicle 5 


25 cc of neutral pure benzol and 25 cc of neutral ethyl alcohol, or 
ethyl alcohol denatured with pure benzol or pure methyl alcohol. 
(The alcohol used in all cases must be neutral.) Boil for 30 
minutes. (It is best to use a reflux condenser.) Cool to room 
temperature, add 4 drops of phenolphthalein indicator solution, 
and titrate with standard alcoholic sodium hydroxide. From 
the number of cubic centimeters of standard hydroxide solution 
calculate the acid number to the basis of the nonvolatile resi- 
due. (Acid number is milligrams of KOH required to neutralize 
acid in 1 g of material tested.) 


4. REAGENT 


ALCOHOLIC SODIUM HYDROXIDE SOLUTION.—Dissolve pure so- 
dium hydroxide in 95 per cent ethyl alcohol in the proportion of 
about 22 gper 1ooocc. Let stand ina stoppered bottle. Decant 
the clear liquid into another bottle and keep well stoppered. 
Standardize against half normal sulphuric or hydrochloric acid, 
using phenolphthalein as indicator. This standardization must 
be made each day that the solution is used. 

This solution should be colorless or only slightly yellow when 
used, and it will keep colorless longer if the alcohol is previously 
treated with sodium hydroxide (about 80 g to 1000 cc) kept at 
about 50° C for 15 days and then distilled. 


5. BASIS OF PURCHASE 


Composite vehicle shall be purchased by volume, the unit being 
a gallon of 231 cubic inches at 15.5° C (60° F). The volume may 
be determined by measure or, in case of large deliveries, it may 
be easier to determine the net weight and specific gravity at 
15.5/15-5° C (60/60° F) of the delivery. The weight per gallon in 
pounds can then be determined by multiplying the specific grav- 
ity by 8.33. The net weight in pounds divided by the weight 
per gallon gives the number of gallons. 


ADDITIONAL COPIES 


OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C, 

AT 


5 CENTS PER COPY 
V 


WASHINGTON : GOVERNMENT PRINTING OFFICH : 1922 


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- DEPARTMENT OF COMMERCE. 


BUREAU OF STANDARDS. 


S. W. STRATTON, Director. 


CIRCULAR OF THE BUREAU OF STANDARDS. 


No. 103. 


[3d edition. Issued July 22, 1922.] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
_ WATER-RESISTING SPAR VARNISH. 


FEDERAL SPECIFICATIONS BOARD. 
STANDARD SPECIFICATION No. 18. 


This Specificat.on was officially adopted by the Federal Specifications Board 
on February 3, 1922, for the use of the Departments and Independent Establish- 
ments of the Government in the purchase of materials covered by it. 


CONTENTS. 
Page 
Iu erAmIO eae. Mtl. Avie. hicah jo aces. malasilacaui died. I 
A oe igs oe cn yo ce ot ead aha wd abieaa on & 2 
Seem COMUNOUUION (oop acess ste es fe aeenwevteeenccecsiebieul cess 2 
ES a ce «age eh ete hd de eeioehis hee ee 6 
1. GENERAL. 


The varnish shall be suitable for use on both outside and inside 
surfaces of vessels, buildings, etc., and must be resistant to air, 
light, and water. The manufacturer is given wide latitude in the 
selection of raw materials and processes of manufacture, so that 
he may produce a varnish of the highest quality. It must meet 
the following requirements: 

APPEARANCE.—Clear and transparent. 

CoLor.—Not darker than a solution of 3 g of potassium dichro- 
mate in 100 cc of pure sulphuric acid, specific gravity 1.84. 

FLasH Point (CLosED-Cup).—Not below 30° C. (85° F.). 

NONVOLATILE MaTrerR.—Not less than 4o per cent by weight. 

112463°—22 


2 Circular of the Bureau of Standards. 


Set to Toucu.—lIn not more than 5 hours. 

Dry Harp AND ToucH.—lIn not more than 24 hours. 

WorKING PROPERTIES.—Varnish must have good brushing, 
flowing, covering, and leveling properties. 

SAFETY OF WorKING.—Varnish must pass the draft test. 

WatTER RESISTANCE.—Dried film must withstand cold water 
for 18 hours and boiling water for 15 minutes without whitening 
or dulling. 

TOUGHNESS.—Varnish must pass a 50 per cent Kauri reduction 
test at 24° C. (75° F.). 

Note.—Deliveries will, in general, be sampled and tested by the soltewille methods, 


but the purchaser reserves the right to use any additional available information to 
ascertain whether the material meets the specification. 


2. SAMPLING. 


It is mutually agreed by buyer and seller that a single package 
out of each lot of not more than 1000 packages be taken as repre- 
sentative of the whole. Whenever possible an original unopened 
container shall be sent to the laboratory, and when for any reason 
this is not done the inspector shall thoroughly mix the contents 
of the container sampled, transfer not less than 1 quart to a clean 
dry glass bottle or tin can, which must be nearly filled with the 
sample, securely stoppered with a new clean cork or well-fitting 
cover or cap, sealed, and distinctly labeled by the inspector. 
The inspector should take a duplicate from the container sampled 
to be held for check in case of dispute, and, when requested, —_* 
take a sample for the seller. 


3. LABORATORY EXAMINATION. 


The tin panels used in the following tests shall all be cut from 
bright tin plate weighing not more than 25 g nor less than 19 g 
per square decimeter (0.51 to 0.39 pound per square foot). (Com- 
mercial No. 31 gage bright tin plate should weigh about 0.44 
pound per square foot. It is important that the tin plate used 
shall be within the limits set.) The panels shall be about 7.5 by — 
13 cm (3 by 5 inches) and must be thoroughly cleaned with benzol 
immediately before using. 

(a) APPEARANCE.—Pour some of the thoroughly mixed sample 
into a clear glass bottle or test tube and examine by transmitted 
light. The varnish must be clear and transparent. 


W ater-resisting Spar Varnish. 3 


(6) CoLor.—Prepare a standard color solution by dissolving 3 
g of pure powdered potassium dichromate in 100 cc of pure con- 
centrated sulphuric acid of specific gravity 1.84. Gentle heat 
may be used if necessary to perfect the solution of the dichromate. _ 
The standard color solution and a sample of the varnish to be 
tested shall be placed in clear thin-walled glass tubes of the same 
diameter. The color comparison shall be made by placing the 
tubes close together and looking through them by transmitted 
light. ‘The tubes used for this test should be 1.5 to 2.0 cm (54 to 
+ inch) in diameter dnd shall be filled to a depth of at least 2.5 
em (1 inch). (Since the potassium dichromate-sulphuric acid 
must be freshly made for this color comparison, it is frequently 
more convenient to compare samples with a permanently sealed 
tube of varnish which has previously been found to be slightly 
lighter in color than the standard solution of 3 g dichromate in 
sulphuric acid. When samples are found to be darker than this 
standard tube of varnish, the dichromate standard should be made 
up for final decision.) 

-(c) Fiasm Pornt.—Determine with either the Tag or Elliott 
closed-cup tester. The former is preferred.’ 

(dq) NONVOLATILE MATTER.—Place a portion of the sample in 
a stoppered bottle or weighing pipette. Weigh container and 
sample. ‘Transfer about 1.5 g of the sample to a weighed flat- 
bottomed metal dish about 8 cm in diameter (a friction-top can 
plug). Weigh container again and by difference calculate the 
exact weight of the portion of sample transferred to the weighed 
dish. Heat dish and contents in an oven maintained at 105 to 
110° C, (221 to 230° F.) for three hours. Cool and weigh. From 
the weight of the residue left in the dish and weight of the sample 
taken calculate the percentage of nonvolatile residue. 

(e) Dryinc Time.—Pour the varnish on one of the tin panels 
described above. Place the panel in a nearly vertical position in 
a well-ventilated room but not in the direct rays of the sun. The 
atmosphere of this room must be free from products of combustion 
or laboratory fumes. ‘The temperature of the room should be | 
from 21 to 32° C..(70 togo° F.). The film is tested at points not 
less than 2.5 em (1 inch) from the edges of the film by touching 
lightly with the finger. The varnish is considered to have set to 
touch when gentle pressure of the finger shows a tacky condition 


1 Directions for using the Tag tester may be found in A. S. T. M. Standards D 56-21, and directions for 
using the Elliott cup in Proceedings A. S. T. M., 1917, part 1, p. 414. 


4 Circular of the Bureau of Standards. 


but none of the varnish adheres to the finger. The varnish is 
considered: to have dried hard when the pressure that can be 
exerted between the thumb and finger does not move the film or 
leave a mark which remains noticeable after the spot is lightly 
polished. If rapid light rubbing breaks the surface, the sample 
is considered not to have satisfactorily dried hard. In case the 
test shows time of setting to touch or drying hard more than 5 
and 24 hours, respectively, two additional tests shall be run on 
different days, and if the varnish does not meet the above drying 
and hardening requirements on both of these additional tests it 
shall be considered unsatisfactory. In cases where different labo-. 
ratories fail to agree on the drying test, due to different atmos- 
pheric conditions, and umpire tests are necessary, such tests:shall 
be made in a well-ventilated room maintained at a WRATH of 
70° F. and relative humidity of 65 per cent saturation. 

(f) Drarr TEst.—Flow the varnish on one of the standard tin 
panels and immediately place the panel in the direct draft of a 
small (8 or 10 inch) electric fan running at full speed. The panel 
should be placed approximately 2 feet from the fan in a nearly 
vertical position and at an angle of 45° to the line of the air 
current. Allow the panel to remain in this position for five hours, 
remove, and allow to harden overnight. ‘The varnish shall show 
no dulling, crow’s footing, or frosting. (This test shall be made 
under the same room and temperature condition noted annie . 
Drying Time.) 


(g) WaTER RESISTANCE.—Pour the varnish on two of et tin E 


panels described above and allow to dry under the conditions 
described in paragraph (e) for 48 hours. Place one of these panels 
in a beaker containing about 2.5 inches of distilled water at room 
temperature (immersing the end of the panel which was upper- 
most during the drying period) and leave in water for 18 hours. 
The varnish shall show no whitening and no more than very slight 
dulling either when observed immediately after removing from 
the water or after drying for two hours.’ Place the other panel 
in a beaker containing about 2.5 inches of boiling distilled water 
(immersing the end of the panel which was uppermost during the 
drying period) and allow to remain in the boiling water for 15 
minutes. The varnish shall show no whitening and no more than | 
a very slight dulling either when observed immediately after 
removing from the water or after drying for two hours. 


eerte ces 6 ieee 


Water-resisting Spar Varnish. 5 


(h) ToucHNEss.—The toughness of the varnish is determined — 
by the Kauri reduction test, as follows: By proportionately re- 
anon its toughness by the addition of a standard solution of 

“run-Kauri ’ gum in pure spirits of turpentine. 

( (2) Preparation of the “Run Kauri. Arrange a distillation 
fee water-cooled condenser, and a tared receiver on a balance. 
| Place in the flask about one-third of its volumetric capacity of 

/ / clear, bright hard pieces of Kauri gum broken to pea size. Care- 
‘| fully melt and distill until 25 per cent by weight of the gum taken 

| is collected in the tared receiver. (At the end of the distillation 
/ the thermometer in the distillation flask with the bulb at the level 
of the discharging point of the flask should register about 316° C. 
(600° F,).) Pour the residue into a clean pan and when cold 
break up into small pieces. 

(2) Preparation of Standard “‘Run Kauri” Solution. —Place.; a 
quantity of the small broken pieces of run Kauri together with 
twice its weight of freshly redistilled spirits of turpentine, using 
only that portion distilling over between 153° and 170° C. (308° and 
338° F.) in a carefully tared beaker. Dissolve by heating to a 
temperature of about 149° C. (300° F.) and bring back to correct 
weight when cold by the addition of the amount of redistilled 
spirits of turpentine necessary to replace the loss by evaporation 
during the dissolving of the gum. 

(3) Reduction of the Varnish.—Having carefully determined the 
nonvolatile content of the varnish according to the method under 
paragraph (d) of this specification, take 100 g of the varnish and 
add to it an amount of the standard run-Kauri solution equivalent 
to 50 per cent, by weight, of the nonvolatile matter in the varnish. 
Mix the varnish and the solution thoroughly. 

(4) Application of the Varnish.—Flow a coat of the varnish 
thus reduced on one of the tin panels described above and let 
stand in a nearly vertical position at room temperature for one 
hour. Next place the panel in a horizontal position in a properly 
ventilated’ oven and bake for five hours at 95 to 100° C. Re- 
move the panel from the oven and allow to cool at room tempera- 
ture, preferably 24° C. (75° F.) for one hour. 

(5) Bending the Panel.—Place the panel with the varnished 
side uppermost over a 3 mm (14-inch) rod, held firmly by suitable 
supports, at a point equally distant from the top and bottom 
edges of the panel and bend the panel double rapidly. The var- 
nish must show no cracking whatsoever at the point of bending. 


6 Circular of the Bureau of Standards. 


For accurate results the bending of the panel should always be 
done at 24° C. (75° F.), for a lowering of the temperature will lower 
the percentage of reduction that the varnish will stand. without 
cracking, while an increase in the temperature increases the per- 
centage of reduction that the varnish will stand. 


4. BASIS OF PURCHASE. 


Varnish shall be purchased by volume, the unit being a gallon 
of 231 cubic inches at 15.5° C. (60° F.). The volume may be 
determined by measure, or, in case of large deliveries, it may be 
easier to determine the net weight and specific gravity at 15.5 /15.5° . 
C. (60/60° F.) of the delivery. The weight per gallon in pounds 
can then be determined by multiplying the specific gravity by — 
8.33. The net weight in pounds divided by the weight per gallon 
gives the number of gallons. ys et 


ADDITIONAL COPIES | 


OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 

AT 


5 CENTS PER COPY. 
V 


DEPARTMENT OF COMMERCE. 
BUREAU OF STANDARDS. 


CIRCULAR OF THE BUREAU OF STANDARDS. 
No. 104. 


[2d Edition. Issued January 30, 1923.] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
ASPHALT GSI a 


ee 


FEDERAL SPECIFICATIONS BOARD. 
STANDARD SPECIF ICATION No. 19. 
[Revised January 2, 1923.] 


This specification was officially adopted by the Federal Specifications Board 
on February 3, 1922, for the use of the departments and independent establish- 
ments of the Government in the purchase of asphalt varnish. 


CONTENTS. 
Page. 
SG ST Fi ee Re ere PEP MRC TEE NT RRR e I 
Ne os ko kn ENE EA BU Oe hs nw ogi es Seiees une 2 
er re er IAT ION ose nn So ea ea des as beac have oeaeeen 3 
MOE eh oh.5 cities: Bae pis Cwstalist 4peh - Foaes ae ad thane is ae 7 
1. GENERAL. 


This varnish shall be composed of a high grade of asphalt 
fluxed and blended with properly treated drying oil and thinned 
to the proper consistency with a volatile solvent. It must be 
resistant to air, light, lubricating oil, water, and, when the con- 
tract so specifies, to mineral acids of the concentration herein- 
after specified. It must meet the following requirements: 

APPEARANCE.—Smooth and homogeneous; no livering or 
stringiness. 

CoLor.—Jet black. 

FLasH Pornt (CLOsED-CuP).—Not below 30° C. (86° F.). 

27817°—23 


2 Circular of the Bureau of Standards. 


AcTION with LINSEED O1L.—Varnish must mix readily to a 
homogeneous mixture with an equal volume of raw linseed oil. 

MarrER INSOLUBLE IN CARBON BISULPHIDE.—Not more than 
I per cent. 

NoNVOLATILE Matter.—Not less than 40 per cent by weight. 

Farry Martrer.—Not less than 20 per cent of the nonvolatile. 
Must be liquid and not show a violet coloration by the Liebermann- 
Storch test. 

Ser to Toucs.—Within 5 hours. 

Dry Harp AND ToucH.—Within 24 hours. 

ToucHNEss.—Film on metal must withstand rapid bending 
over a rod 3 mm (% inch) in diameter. 

WoRKING PROPERTIES.—Varnish must heve good brushing, 
flowing, covering, and leveling properties. 

RESISTANCE TO WATER.—Dried film must withstand cold water 
for 18 hours. 

RESISTANCE TO O1L.—Dried film must withstand lubricating 
oil for 6 hours. 

RESISTANCE TO MringERAL Acips.'—Dried film. must withstand 
action of the following acids for six hours: Sulphuric acid, specific 
gravity 1.25 (about 33 per cent). Nitric acid, specific gravity 
1.12 (about 20 per cent). Hydrochloric acid, specific gravity 
1.09 (about 18 per cent). Bets. 

NoTe.—Deliveries will, in general, be sampled and tested by the following methods, 


but the purchaser reserves the right to use any additional available information to 
ascertain whether the material meets the specification. 


2. SAMPLING. 


It is mutually agreed by buyer and seller that a single package 
out of each lot of not more than 1,000 packages be taken as repre- 
sentative of the whole. Whenever possible, an original unopened 
container shall be sent to the laboratory. When for any reason this 
can not be done, the inspector shall select a package and thoroughly ~ 
mix its contents. He shall fill a 1 quart, clean, dry container from 
this package, securely stopper it with a new clean cork or well- 
fitting cover or cap, seal, and distinctly label it. The inspector 
shall take a duplicate from the container sampled to be held for 
check in case of dispute, and, when requested, shall take a sample 
for the seller. 


1 Only required when the contract specifically demands asphalt varnish that is resistant to mineral acids. 


Specification for Asphalt Varnish. 3 
3. LABORATORY EXAMINATION. 


(a) APPEARANCE AND CoLOor.—Pour some of the thoroughly 
mixed sample on a clean, clear glass plate and stand in a vertical 
position until the excess varnish has drained off. Examine the 
film by transmitted light. The varnish must be smooth and 
homogeneous and must not show any separation or segregation 
of the constituents. Examine the film by reflected light. The 
film must be jet black in color. 

(6) FLasH Pornt.—Determine with either: the “Tag” or 
Elliott closed-cup tester. ‘The former is preferred.” 

(c) ACTION WITH LINSEED O1L.—Pour 10 ce of the varnish 
into a test tube and add an equal volume of raw linseed oil con- 
forming to Bureau of Standards Circular No. 82. Stopper the 
test tube and shake vigorously for several minutes. Then pour 
some of the mixture on a clear glass plate and stand in a vertical 
position. After the excess varnish has drained off examine the 
film by transmitted light. There shall be no separation of the 
oil and varnish. 

(d) MATTER INSOLUBLE IN CARBON BISULPHIDE.—Weigh about 
5 g of the varnish into a small beaker, add 25 cc of carbon bisul- 
phide, and allow to stand for 15 minutes. Filter through a 
weighed Gooch crucible, prepared with a medium thick mat of 
asbestos, using suction if necessary to aid in filtration. Wash 
the residue in the crucible with carbon bisulphide until the wash- 
ings are colorless. Dry in air at room temperature until the odor 
of carbon bisulphide has almost disappeared, and then for one 
hour in an oven at 110°C. Cool and weigh. From the weight of 
the insoluble left in the crucible and the weight of sample taken 
calculate the percentage of insoluble in carbon bisulphide. 

(e) NONVOLATILE MATTER.—Place a portion of the sample in a 
stoppered bottle or weighing pipette. Weigh the container and 
sample. ‘Transfer about 1.5 g of the sample to a weighed flat- 
bottomed metal dish about 8 cm in diameter (a friction-top can 
plug). Weigh the container again and by difference calculate the 
exact weight of the portion of sample transferred to the weighed 
dish. Heat the dish with its contents in an oven maintained at 
105 to 110° C. for three hours. Cool and weigh. From the 
weight of the residue left in the dish and the weight of the sample 
taken calculate the percentage of nonvolatile residue. 


2 Directions for using the ‘‘Tag”’ tester may be found in A. S. T. M. Standards Ds6-21, and directions 
for using the Elliott cup in Proceedings A. S. IT. M., 191r7,-pt. 1, D. 414. 


4 Circular of the Bureau of Standards. 


(f) Farry MatTrer.—Weigh about 5 g of the varnish into a 
wide-mouthed flask, add 50 ce of benzol and 5 g of clean, fine 
silica sand and heat under a reflux condenser on a steam bath 
until the varnish is entirely dissolved. Add 25 cc of ethyl alcohol 
denatured with methyl alcohol and 25 cc of a 0.5 N alcoholic 
caustic soda solution and continue boiling under the reflux con- 
denser for one-half hour. Remove the condenser and evaporate 
the solution to dryness. Add to the residue in the flask 50 ce of 
distilled water and heat until the residue is disintegrated. Filter 
the water solution of the soaps. Repeat this operation with 25 
cc portions of water until the residue is completely eh a Ow 
and the wash water is clear and colorless. 

Combine the filtrates (the soap solution and washings), acidify 
with hydrochloric acid, and heat until the fatty acids and any 
emulsified asphalt separate and rise to the top and the water 
below is clear. Cool, transfer to a separatory funnel, and extract 
three times with 25 cc portions of ether. Combine the ether ex- 
tracts and wash with water until free from acid. Filter the ether 
extracts through paper into a beaker and wash the residue on the 
paper with ether imtil the washings run through colorless. Evap- 
orate the ether solutions to dryness. 

Add ro to 15 cc of 95 per cent ethyl alcohol to the residue in 
the beaker and warm on the steam bath. Cool to room tempera- 
ture and filter through paper into a tared flask or dish. Repeat 
this operation with 5 cc portions of 95 per cent ethyl alcohol 
until the alcohol remains colorless. Finally wash the residue on 
the paper with 95 per cent ethyl alcohol until the washings run 
through colorless. Evaporate the alcoholic solution to dryness on 
a steam bath and heat for an hour in an oven at 105° C. (221° F.). 
Cool and weigh. From the weight of the résidue in the flask and 
the weight of the original sample calculate the aabaithe 5 of fatty 
matter. 

(Sometimes the residue obtained after ca potheaen and the 
evaporation of the benzol and alcohol from the saponifying mix- 
ture is not completely disintegrated by boiling with water. In 
that case extract with water until nothing further dissolves and 
then dry. Dissolve in benzol, using heat if necessary, and wash 
the benzol solution several times with water. Heat the washings 
until the odor of benzol has disappeared and add to the soap 
solution before acidifying.) 

The fatty matter obtained above must be a clear amber colored 
liquid. A fugitive violet color shall not be obtained when the 


Specification for Asphalt Varnish. 5 


fatty matter is subjected to the following test: Dissolve a small 
amount of the fatty matter in 5 cc of acetic anhydride, warming 
if necessary to aid solution. Cool, draw off the acetic anhydride 
solution, and add a drop of sulphuric acid, 1.53 specific gravity. 

(g) Dryinc TimE.—Pour the varnish on a clean glass plate 
not less than 15 cm (6 inches) long and 10 cm (4 inches) wide. 
Place the plate in a nearly vertical position in a well-ventilated 
room, but not in the direct rays of the sun. The temperature of 
the room should be from 21 to 32° C. (70 to 90° F.). ‘Test the 
film at points at not less than 2.5 cm (1 inch) from the edges of the 
film by touching lightly with the finger. The varnish is considered 
to have set to touch when gentle pressure of the finger shows a 
tacky condition, but none of the varnish adheres to the finger. 
The varnish is considered to have dried hard when the pressure 
that can be exerted between the thumb and finger does not move 
the film or leave a mark which remains noticeable after the spot 
is lightly polished. If rapid light rubbing breaks the surface, the 
sample is not considered to have satisfactorily dried hard. In 
case the test shows time of setting to touch or drying hard more 
than 5 and 24 hours, respectively, two additional tests shall be 
run on different days, and if the varnish does not meet the above 
drying and hardening requirements on both of these additional 
tests it shall be considered unsatisfactory. In cases where dif- 
ferent laboratories fail to agree on the drying test, due to different 
atmospheric conditions, and umpire tests are necessary, such tests 
shall be made in a well-ventilated room maintained at a tempera- 
ture of 70° F. and relative humidity of 65 per cent saturation. 

(h) ‘TouGHNESs.—Flow the varnish on one side of a dry steel 
plate that has previously been cleaned of all scale, rust, and grease, 
This plate should be about 0.4 mm (0.016 inch) thick, and 10 by 
I5 cm (4 by 6 inches) will be found of convenient size. Let the 
test piece dry in a vertical position, not in the direct rays of the 
sun, in a well-ventilated room at a temperature not below 21° C. 
(70° F.) for a period of not less than six days. Now bring the 
test piece to a temperature between 21 and 24° C. (70 to 75° F.) 
and, with the varnish film on the outside, bend rapidly over a rod 
3 mim (3% inch) in diameter. The film must show no evidence of 
cracking or flaking. 

(2) WORKING PRoOPERTIES.—A clean piece of steel plate similar 
to that used for testing the toughness of the varnish shall be used 
for determining the working properties. The plate shall be 
thoroughly cleaned of all grease and rust and dried. It shall 


6 Circular of the Bureau of Standards. 


then be Jaid in a horizontal position and one coat of the varnish 
applied by brushing. The varnish shall work easily under the 
brush, showing no tendency to draw or pull, and shall flow out 
to a smooth, glossy, jet-black film, free from brush marks, blisters, 
pinholes, or other defects. Test pieces prepared in the above 
manner and allowed to dry in a horizontal position, not in the 
direct rays of the sun, in a well-ventilated room, at a temperature | 
not below 21° C. (70° F.) for a period of not less than six days, 
shall be used for testing the resistance of the varnish to cold water 
and lubricating oil. 

(j) RESISTANCE TO WaTER.—A test piece, prepared and dried 
as under (2), shall be inclined at an angle of 45° to the vertical, 
and a gentle stream of cold tap water with a temperature of 
about 25° C. (77° F.) allowed to flow for 18 hours down the middle 
of the varnished surface. After wiping off with a soft cloth or 
chamois skin any deposit due to the tap water the varnish must 
show no whitening, dulling, softening, or other visible defects. 

(k) RESISTANCE TO LUBRICATING O1L.—A test piece prepared 
and dried as under (1) shall be laid flat, and in at least two different 
places several drops of locomotive engine lubricating oil * allowed 
to stand in contact with the film for six hours. During the test 
the spots of oil shall be covered with small watch glasses. After 
wiping off the oil with cotton waste no softening or other deteri- 
oration of the film due to the lubricating oil shall be perceptible. 

(1) RESISTANCE TO MINERAL Acip.—A piece of dry, steel plate 
free from scale, rust, and grease shall be used for this test. It 
shall be laid in a horizontal position and one coat of the varnish 
applied by brushing. This coat of varnish shall then be allowed 
to dry for 24 to 48 hours, when a second coat shall be applied. 
The second coat shall be allowed to dry, as in (2), for a period of 
not less than six days before testing. The test pieces shall then 
be laid flat and in different places several drops each of sulphuric 
acid, specific gravity 1.25, nitric acid, specific gravity 1.12, and 
hydrochloric acid, specific gravity 1.09, shall be allowed to remain 
on the surface of the film for six hours at room temperature, 
about 21° C. (7o° F.). During the test the drops of acid shall be 
covered with small watch glasses to prevent evaporation. After 
six hours the acid shall be washed off with tap water, and after 
drying for one hour the spots previously in contact with the acid 
examined. They shall show no appreciable change in hardness. 


8 A straight mineral oil having a viscosity (Saybolt Universal) of about 75 sec. at 210° F. 


Specification for Asphalt Varnish. yi 


The film shall then be allowed to dry for 12 hours, when it shall 
again be examined. The spots exposed to the acid shall show 
no disintegration or browning, and their luster shall not be im- 
paired. A slight bloom around the area of the spot exposed to 
the acid shall not be considered an indication of failure. ‘The 
film shall then be removed with carbon tetrachloride, chloroform, — 
or carbon bisulphide and the metal examined. It shall show no 
corrosion. 
4. BASIS OF PURCHASE. 


Asphalt varnish shall be purchased by volume, the unit being 
a gallon of 231 cubic inches at 15.5° C. (60° F.). The volume may 
be determined by measure or, in case of large deliveries, it may be 
easier to determine the net weight and specific gravity at 15.5/15.5° 
C. (60/60° F.) of the delivery. The weight per gallon in pounds 
can then be determined by multiplying the specific gravity by 
8.33. The net weight in pounds divided by the weight per gallon 
gives the number of gallons. 7 

WASHINGTON, January 2, 1923. 


ADDITIONAL COPIES 
OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 


AT 
5 CENTS PER COPY 


PURCHASER AGREES NOT TO RESELL OR DISTRIBUTE THIS 
COPY FOR PROFIT.—PUB. RES. 57, APPROVED MAY 11, 1922 


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DEPARTMENT OF COMMERCE. 
BUREAU OF STANDARDS. 
S. W. STRATTON, Director. 


CIRCULAR OF THE BUREAU OF STANDARDS. 


No. 105. 


[2d edition. September 18, 1922.] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
LIQUID PAINT DRIER. 


ao 


FEDERAL SPECIFICATIONS BOARD. 
STANDARD SPECIFICATION No. 20. 


This specification was officially adopted by the Federal Specifications Board on 
February 3, 1922, for the use of the departments and independent establishments of 
the Government in the purchase of materials covered by it. 


CONTENTS. 


I 

2 

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a wikis bs Maur d eicwicagt ds hee oaetirs. oul Oey. fled, md 


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1. GENERAL. 


This specification applies both to straight oil drier—that is, 
material free from resins or ‘“‘gums’’—and to Japan drier; that is, 
material containing varnish ‘‘gums.”’ 

The drier shall be composed of lead, manganese, or cobalt, or 
a mixture of any of these elements combined with a suitable fatty 
oil, with or without resins or ‘‘ gums,’ and mineral spirits or tur- 
pentine, or a mixture of these solvents. It shall be free from 
sediment and suspended matter. ‘The drier when flowed on metal 
and baked for 2 hours at 100° C. (212° F.) shall leave an elastic 
film. ‘The flash point shall be not lower than 30° C. (85° F.) when 
tested in a closed-cup tester. It shall mix with pure raw linseed 

7789°—22 


2 Circular of the Bureau of Standards 


oil in the proportion of 1 volume of drier to 19 volumes of oil with- 
out curdling, and the resulting mixture when flowed on glass shall 
dry in not more than 18 hours. When mixed with pure raw lin- 
seed oil in the proportion of 1 volume of drier to 8 volumes of oil, 
the resulting mixture shall be no darker than a solution of 6 g of 
potassium dichromate in 100 cc of pure sulphuric acid of specific 
gravity 1.84. 

Note.—Deliveries will, in general, be sampled and tested by the following meth- 


ods, but the purchaser reserves the right to use any additional available information 
to ascertain whether the material meets the specification. 


2. SAMPLING. 


It is mutually agreed by buyer and seller that a single package 
out of each lot of not more than 1,000 packages be taken as repre- 
sentative of the whole. Whenever possible, an original unopened 
container shall be sent to the laboratory, and when for any reason 
this is not done, the inspector shall thoroughly mix the contents 
of the container sampled, transfer not less than 1 quart to a clean, 
dry glass bottle or tin can which must be nearly filled with the 
sample, securely stoppered with a new clean cork or well-fitting 
cover or cap, sealed, and distinctly labeled by the inspector. ‘The 
inspector should take a duplicate from the container sampled to be 
held for check in case of dispute, and, when requested, should take 
a sample for the seller. 


3. LABORATORY EXAMINATION. 


(a) SEDIMENT AND SUSPENDED MATTER.—Thoroughly mix the 
sample. Fill two test tubes of the same size (15 em, or 6 inches) 
to within 2.5 cm (1 inch) of the top with the sample. Stopper 
the tubes with clean corks. Let stand for 24 hours. Note 
whether sediment is evident in the tubes; if not, shake one tube 
vigorously and compare the two tubes. If they still look alike, 
the sample is considered free from sediment and suspended matter. 

(6) CoLor.—Mix 2 ce drier and 16 ce clear pure raw linseed oil 
that complies with the specifications of B. S. Circular No. 82. Dis- 
solve 6 g of pure powdered potassium dichromate in 100 ce of pure 
concentrated sulphuric acid (specific gravity 1.84). Gentle heat 
may be used if necessary to secure a perfect solution of the di- 
chromate. This solution should be freshly prepared. The color 
comparison shall be made by placing the 1:8 drier-linseed oil mix- 
ture and the dichromate-sulphuric acid solution in thin-walled 
glass tubes of the same diameter, 1.5 to 2 cm (5% to 18 inch) to 


U. S. Government Specifications jor Liquid Patnt Drier. 3 


depths of at least 2.5 cm (1 inch) and comparing the depth of 
color by looking through the tubes across the column of liquid by 
transmitted light. 

(c) MIxING wirH LINSEED OL, SETTING To ToucH, AND 
DRYING.—Mix 1 cc of the sample and 19 cc of clear pure raw 
linseed oil that complies with the specifications of B. S. Circular 
No. 82. Thoroughly clean a glass plate, finally washing with 
benzol and drying. Pour a portion of the mixture of linseed oil 
and drier over this plate and place the plate in a vertical position 
in a well-ventilated room, the atmosphere of which is free from 
products of combustion or laboratory fumes. Allow the remainder 
of the mixture to stand for 2 hours. No sediment or precipitate 
should appear. At 1-hour intervals examine the film of oil on 
the plate by touching it lightly with the finger at points not less 
than 2.5 cm (1 inch) from the edges. If the film still has the 
greasy feel of fresh linseed oil, it has not set to touch. If the film 
feels tacky and adheres to the finger, it is considered to have set 
to touch. If the finger can be drawn lightly across the film with- 
out the oil sticking to the finger or the surface being marred by 
this treatment, the oil is considered dry. In case the test shows 
time of setting to touch or drying greater than 8 and 18 hours, 
respectively, a second test shall be run on a different day and the 
average of the two tests taken. 

(2) NATURE OF BAKED F 1L1M.—Thoroughly clean with benzol a 
piece of bright sheet metal, either bright sheet iron, tin plate, or 
terneplate. Shake the sample of drier thoroughly and flow enough 
on the plate so that a space at least 7.5 cm (3 inches) wide is cov- 
ered. Allow the plate to stand in a vertical position at room tem- 
perature for 30 minutes and then hang in an oven ata temperature 
of 100 to 105° C. (212 to 221° F.) for 2 hours. 

Remove the plate from the oven and allow it to stand at room 
temperature for not less than.1 hour. ‘Test the film of drier with 
a knife blade at a point not less than 2.5 cm (1 inch) from the edge. 
If the film powders or particles fly under the knife blade, it will be 
considered brittle, which will be cause for rejection. 

(e) FLasn Pornt.—Determine with either the “Tag” or Elliott 
closed-cup tester. The former is preferred. 


1 Directions for using the Tag tester may be found in A.S. T. M. Standards D 56-21, and directions for 
using the Elliott cup in Proceedings A. S. T. M., 1917, pt. 1, p. 414. 


A Circular of the Bureau of Standards 
4. BASIS OF PURCHASE. 


Drier shall be purchased by volume, the unit being a gallon of 
231 cubic inches at 15.5° C. (60° F.). ‘The volume may be deter- 
mined by measure or, in case of large deliveries, it may be easier to 
determine the net weight and specific gravity at 15.5/15.5° C. 
(60/60° F.) of the delivery. The weight per gallon in pounds can 
then be determined by multiplying the specific gravity by 8.33. 
The net weight in pounds divided by the weight per gallon gives 
the number of gallons. 


——_—_————————— 
ADDITIONAL COPIES 
OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 
AT 
5§ CENTS PER COPY 


V 


DEPARTMENT OF COMMERCE. 
BUREAU OF STANDARDS. 


S. W, STRATTON, Director. 


CIRCULAR OF THE BUREAU OF STANDARDS. 
No. 111. 


[2d edition, Issued June 24, 1922.] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
FLAT INTERIOR LITHOPONE PAINT, WHITE 
AND LIGHT TINTS. 


FEDERAL SPECIFICATIONS BOARD. 
STANDARD SPECIFICATION No. 21. 


This Specification was officially adopted by the Federal Specifications Board 
on February 3, 1922, for the use of the Departments and Independent Establish- 
ments of the Government in the purchase of materials covered by it. 


CONTENTS, — 
Page 
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1. GENERAL. 


This specification covers ready-mixed lithopone paints, fre- 
quently known as flat, washable wall paint, in white and a variety 
of light tints. Paints under this specification are not intended 
for outside exposure; they ‘shall dry to dead flat opaque coats 
that will adhere well to wood, metal, and plaster, stand washing 
with soap and water, and show no material change in color on 
exposure to light. 

The paint shall be purchased by volume (231 cubic inches to 
the gallon). 


109853°—22 


2 Circular of the Bureau of Standards 


(a) PicmMent.—The pigment shall consist of: 


Maximum. Minimum. 


Per cent. | Per cent. 
80 


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Tinting and extending pigments. ............... ccc c cece eee ee eee e eee eee e ne eeares aS i eaerre: oy! 
Material BBL Die Ate WALCO cos, ow inc dc ial ethce meolass'9 as ibaa os aaeuachis «4, win» ale cetera * ADB abs ere eeaen 


N OTE. —The lithopone used must contain not less than 26 per cent of zinc sulphide and must not darken 
on exposure. 


(6) Liguip.—The liquid ee of the paint shall consis of 
treated drying oils or varnish, or a mixture thereof, and turpentine 
or volatile mineral spirits, or a mixture thereof, in such proportions 
as to insure not less than 25 per cent of nonvolatile vehicle. The 
nonvolatile vehicle shall dry to a tough and elastic film. 

(c) Parnt.—The paint shall be well ground, shall not settle 
badly, cake, or thicken in the container, shall be readily broken 
up with a paddle to a smooth, uniform paint of brushing con- 
sistency, and shall dry within 18 hours to a dead flat finish without 
streaking, running, or sagging and free from laps and brush 
marks. ‘The color and hiding power when specified shall be equal 
to those of a sample mutually agreed upon by buyer and seller. 
After drying for not less than five days, marks made on the painted 
surface with a soft lead pencil (No. 2 Mogul) shall be easily removed 
by washing with soap and warm water without appreciably 
marring the paint surface. The weight per gallon shall be not 
less than 14% pounds. 

The paint shall consist of: 


_ | Maximum, Minimum. 


Per cent. | Per cent. 
7 68 


tee Sy AECL SE EET Creer ee se 2 

Liquid ocaninisa at least 25 per cent nonvolatile matter)...................c.-00: 4 28 

Contes particles and “skins” (total residue retained on No. 325 screen basedon| §8 | — 
plgrizent) ie... «a un debinho cdailte pike gains Hsp es keane) dima RE ee) sere 


NotE.—Deliveries will, in general, be sampled and tested by the following methods, 
but the purchaser reserves the right to use any additional available information to 
ascertain whether the material meets the specification. 


2. SAMPLING. 


It is mutually agreed by buyer and seller that a single package 
‘out of each lot of not more than 1,000 packages shall be taken as 
representative of the whole. Whenever possible, an ‘original 
unopened container shall be sent to the laboratory, and when this 
is for any reason not done the inspector shall determine by thor- 


Specification for Flat Interior Lithopone Paint 3 \ 


ough testing with a paddle or spatula whether the material meets 
the requirement regarding caking in the container. He shall 
then thoroughly mix the contents of the container and draw a 
sample of not less than 5 pounds. This sample shall be placed 
in a clean, dry metal or glass container, which it must nearly fill. 
The container shall be closed with a tight cover, sealed, marked, 
and sent to the laboratory for test with the inspector’s report 
on caking. 

When requested, a duplicate sample may be taken from the 
same package and delivered to the seller, and the inspector may 
take a third sample to hold for test in case of dispute. 


3. LABORATORY EXAMINATION. 


(a) .CAKING IN CONTAINER.—When an original package is re- 
ceived in the laboratory it shall be weighed, opened, and stirred 
with a stiff spatula or paddle. ‘The paint must be no more difficult 
to mix to a uniform consistency than a good grade of flat paint. 
The paint shall finally be thoroughly mixed, removed from the con- 
tainer, and the container wiped clean and weighed. This weight 
subtracted from the weight of the original package gives the net 
weight of the contents. A portion of the thoroughly mixed paint 
shall be placed in a clean container and portions for the remaining 
tests promptly weighed out. 

(6) Cotor.—Place some of the paint on a clean, clear glass plate. 
Place some of the standard agreed upon beside the sample on the 
plate, turn the glass over, and compare the colors. 

(c) WEIGHT PER GALLON.—Weigh a clean, dry, 100 ce gradu- 
ated flask. Fill to the mark with the thoroughly mixed paint and 
weigh again. ‘The increase in weight expressed in grams, divided 
by 100, gives the specific gravity, which multiplied by 8.33 gives 
the weight in pounds per gallon. 

(2) BRUSHING PROPERTIES, TIME OF DRYING, AND RESISTANCE 
T0 WasHING.—Brush the well-mixed paint on a suitable panel, 
which may be ground glass, steel, or well-filled wood. Note 
whether the paint works satisfactorily under the brush. Place 
the panel in a vertical position in a well-ventilated room and let it 
stand for 18 hours. The paint should be dry and free from streaks. 

Let the panel stand for five days, then make marks on it with a 
soft lead pencil (No. 2, Mogul) and wash these marks off with warm 
(75° C.) distilled water and white floating soap, using a sponge or 
soft rag. The marks must be removed by this treatment without 
appreciably marring the paint film. 


4 Circular of the Bureau of Standards 


(e) FastNEss To Licur.—Apply a sufficient number of coats 
of the paint to a ground-glass plate to completely hide the surface, 
cover half of this painted surface with opaque black paper, and 
exposure indoors in a well-lighted room for five days. Remove the 
black paper and examine the surface. The exposed portion should 
be no darker than the portion protected by the black paper. 

({) WaTER.—Mix 100 g of the paint in a 300 cc flask with 75 
ce of toluol. Connect with a condenser and distil until about 
50 ce of distillate has been collected in a graduate. The tem- 
perature in the flask should be then about 105 to 110° C. The 
number of cubic centimeters of water collecting under the toluol 
in the receiver is the percentage of water in the paint. Material | 
complying with the specification should yield less than 1.0 cc. 

(g) VOLATILE THINNER.—Weigh accurately from 3 to 5 g of 
the paint into a tared flat-bottomed dish about 5 cm in diameter, 
spreading the paint over the bottom. Heat at 105 to 110° C. for 
one hour, cool, and weigh. Calculate the loss in weight as per- 
centage of water and volatile thinner, subtract from this the per- 
centage of water (3 (f)), and report the remainder as volatile 
thinner. 

_ (h) PERCENTAGE OF PIGMENT.—Weigh accurately about 15 g 
of the paint into a weighed centrifuge tube. Add 20 to 30 cc of 
“extraction mixture’’ (see Reagents), mix thoroughly with a glass 
rod, wash the rod with more of the extraction mixture, and add 
sufficient of the reagent to make a total of 60 cc in the tube, 
Place the tube in the container of a centrifuge, surround with 
water, and counterbalance the container of the opposite arm 
with a similar tube or a tube with water. Whirl at a moderate 
speed until well settled. Decant the clear supernatant liquid. 
Repeat the extraction twice with 40 ce of extraction mixture and 
once with 4o cc of ether.- After drawing off the ether, set the 
tube in a beaker of water at about 80° C. or on top of a warm 


~. oven for 10 minutes, then in an oven at 110 to 115° C. for two 


hours. Cool, weigh, and calculate the percentage of pigment. 
Grind the pigment to a fine powder, pass through a No. 80 screen 
to remove any skins, and preserve in a stoppered bottle. Pre- 
serve the extracted vehicle for 3 (7). 

(2) PERCENTAGE OF NONVOLATILE VEHICLE.—Add together the 
percentages of water (3 (f)), of volatile thinner (3 (g)), and of pig- 
ment (3 (h)), and subtract the sum from 100. ‘The remainder is 
the percentage of nonvolatile vehicle, which should be not less 
than one-third as large as the percentage of volatile thinner. 


Specification for Flat Interror Lithopone Paint 5 


(j) NaTuRE oF NONVOLATILE VEHICLE.—Evaporate the ex- 
tracted vehicle and extraction mixture from 3 (h) to about 5 cc 
Thoroughly clean with benzol a piece of bright sheet iron, tin 
plate, or terneplate. Spread a portion of the concentrated ex- 
tracted vehicle on the sheet of metal, allow to dry for 30 minutes 
at room temperature in a vertical position, bake for three hours . 
at 100 to 110° C. (212 to 221° F.), remove from the oven, and 
keep at room temperature for three days. Test the film with a 
knife blade at a place not less than 2.5 cm (1 inch) from the edge. 
The film should be tough and elastic; if it powders or if particles 
fly under the test, it will be considered brittle, which will be cause 
for rejection. The film must also stand light, vigorous rubbing 
with the finger without powdering or disintegrating. 

(k) COARSE PARTICLES AND SKINS.—Dry in an oven at 105 to 
110° C. a No. 325 screen, cool, and weigh accurately. Weigh an 
amount of paint containing 10 g of pigment (see 3 (h)), add 50 cc 
of kerosene, mix thoroughly, and wash with kerosene through the 
screen, breaking up all lumps, but not grinding. After washing 
with kerosene until all but the particles too coarse to pass the 
screen have been washed through, wash all kerosene from the 
screen with ether or petroleum ether, heat the screen fm one hour 

at 105 to 110° C., cool, and weigh. 


4. ANALYSIS OF PIGMENT. 


Use the pigment extracted in 3 (h). 

(a) QUALITATIVE ANALYsIs.—Make qualitative sel Si fol- 
lowing ordinary methods. 

(6) MATTER SOLUBLE IN WATER. ashipe nice 2.5 g of the pig- 
ment to a graduated 250 cc flask, add 100 ce of water, boil for 
five minutes, cool, fill to mark with water, mix, and allow to 
settle. Pour the supernatant liquid through a dry filter paper 
and discard the first 20 cc. Then evaporate 100 cc of the clear 
filtrate to dryness ina weighed dish, heat for one hour at 105 to 
110° C., cool, and weigh. ‘The residue should not exceed 0.008 g. 

(c) BaRIuM SULPHATE AND SILICEOUS’ MaTERIAL.—Transfer 
1 g of pigment to a porcelain casserole or dish, moisten with a 
few drops of alcohol, add 40 cc of hydrochloric acid (1.1, specific 
gravity), cover, and boil to expel hydrogen sulphide; remove the 
cover and evaporate to dryness on the steam bath, moisten with 
hydrochloric acid, dilute with water, filter through paper, and 
wash with dilute hydrochloric acid and then with hot water until 


6 Circular of the Bureau of Standards 


the washings are free from zinc and chlorine. Ignite and weigh 
the residue, which will be barium sulphate and siliceous material. 

Mix the ignited residue with about 10 times its weight of anhy- 
drous sodium carbonate (grind the mixture in an agate mortar if 
necessary), fuse the mixture in a covered platinum crucible, heat- 
ing about one hour. Let cool, place the crucible and cover in a 
250 cc beaker, add about 100 cc of water, and heat until the 
melt is disintegrated. Filter on paper (leaving the crucible and 
cover in the beaker) and wash the beaker and filter thoroughly 
with hot water to remove soluble sulphates. Place the beaker 
containing the crucible and cover under the funnel, pierce the — 
filter with a glass rod, and wash the carbonate residue into the 
beaker by means of a jet of hot water. Wash the paper with 
hot dilute hydrochloric acid (1:1), and then with hot water. If 
the carbonate residue is not completely dissolved, add sufficient 
dilute hydrochloric acid to effect solution, and remove the crucible » 
and cover, washing them with a jet of water. Heat the solution 
to boiling and add 1o to 15 cc of dilute sulphuric acid, and 
continue the boiling for 10 or 15 minutes longer. Let the pre- 
cipitate settle, filter on a weighed Gooch crucible, wash with hot 
water, ignite, cool, and weigh as BaSO,. Subtract from the re- 
sult of the previous determination to obtain the siliceous material. 

(d) Tota, Zinc CALCULATED As Zinc OximpE.—With material 
containing no interfering elements (iron, for example) weigh ac- 
curately about 1 g of pigment, transfer to a 400 cc beaker, 
moisten with alcohol, add 30 ce of hydrochloric acid (1:2), 
boil for two to three minutes, add 200 cc of water and a small 
piece of litmus paper; add strong ammonia until slightly alka- 
line, render just acid with hydrochloric acid, then add 3 ce of 
strong hydrochloric aeid, heat nearly to boiling, and titrate with 
standard ferrocyanide as in standardizing that solution (see 
Reagents). Calculate total zine as zinc oxide. 

When iron or other interfering elements are present (see 4 (a) ), 
take the filtrate containing the zinc from 4 (c), add a slight excess 
of bromine water and 2 g ammonium chloride, heat to nearly 
boiling, add an excess of ammonia, heat for about two minutes, 
filter, dissolve the precipitate in hydrochloric acid, add 2 g of 
ammonium chloride, and reprecipitate with ammonia as above. 
Filter, wash the precipitate with hot 2 per cent ammonium-chloride 
solution, unite the two filtrates, and determine zinc as above. 


1 


Specification for Flat Interior Lithopone Paint 7 


(e) Zinc Oxipe.—Weigh accurately 2.5 g¢ of pigment, transfer 
to a 250 cc graduated flask, moisten with a few drops of alcohol, 
add about 200 ce of 1 to 3 per cent acetic acid, shake vigorously 
and let stand for 30 minutes, shaking once every five minutes. 
Fill to the mark with 1 to 3 per cent acetic acid, mix, filter through 
a dry paper, discard the first 25 cc and determine zine in 100 cc 
of the filtrate (corresponding to 1 g) as in 4 (d). Calculate the 
_ percentage of zinc oxide. 

(f) CaLcuLations.—Subtract the percentage of zinc oxide 
(4 (e) ) from the percentage of total zinc as zinc oxide (4 (d) ) and 
multiply the remainder by 1.2 to convert to percentage of zinc 
sulphide. In case the percentage of barium sulphate (4 (c)) iis 
not more than 2.86 times as great as the percentage of zinc sul- 
phide, add the two together and call the sum the percentage of 
lithopone. If the percentage of barium sulphate is greater than 
this amount, take 2.86 times the percentage of zinc sulphide as 
the percentage of barium sulphate to be included in the percentage 
of lithopone and include the remainder in the percentage of tinting 
and extending pigments. Subtract, the sum of the percentage of 
zine oxide (4 (e) ), lithopone, and matter soluble in water (4 (0) ) 
from 100. Call the remainder percentage of tinting and extending 
pigments. 

5. REAGENTS. 


(a) Extracrion MixtuRE.— 

3 10 volumes ether (ethyl ether). 
6 volumes benzol. . 
4 volumes methyl alcohol. 
I volume acetone. 

(6) ONE To THREE PER Cen? Acetic “Acip.—Dilute 20 cc 
glacial acetic acid to 1,000 cc with distilled water. 

(c) Uranyt InpicaTor For Zinc TirraTIon.—A 5 per cent 
solution of uranyl nitrate in water or a 5 per cent solution of 
uranyl acetate in water made slightly acid with acetic acid. 

(dq) StanDaRD Potasstum FERROCYANIDE.—Dissolve 22 g. of 
the pure salt in water and dilute to 1,000 cc. To standardize, 
transfer about 0.2 g (accurately weighed) of pure metallic zinc or 
freshly ignited pure zinc oxide to a 400 cc beaker. Dissolve in 
10 cc of hydrochloric acid and 20 cc of water. Drop in a small 
piece of litmus paper, add ammonium hydroxide until slightly 
alkaline, then add hydrochloric acid until just acid, and then 3 cc. 


8 Circular of the Bureau of Standards 


of strong hydrochloric acid. Dilute to about 250 ce with hot’ 
water and heat nearly to boiling. Run in the ferrocyanide solu- 
tion slowly from a burette with constant stirring until a drop 
tested on a white porcelain plate with a drop of the uranyl indi-_ 
cator shows a brown tinge after standing one minute. A blank 
should be run with the same amounts of reagents and water as in 
the standardization. The amount of ferrocyanide solution re- 
quired for the blank should be subtracted from the amounts used 
in standardization and in titration of the sample. The standardi- 
zation must be made under the same conditions of temperature, 
volume, and acidity as obtain when the sample is titrated. 


SA SSSR TSS LS SAE TSI ASST AEST SNC Soa | 


ADDITIONAL COPIES 
OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D, C. 


AT 
5 CENTS PER COPY 
Vv 


DEPARTMENT OF COMMERCE. 
BUREAU OF STANDARDS. 


S. W. STRATTON, Director. 


CIRCULAR OF THE BUREAU OF STANDARDS. 


No. 117. 


[2d edition. Issued July 3, 1922.] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
| INTERIOR VARNISH. 


FEDERAL SPECIFICATIONS BOARD. 
STANDARD SPECIFICATION No, 22. 


This Boeifcation was officially adopted by the Federal Specifications Board on 
February 3, 1922, for the use of the Departments and Independent Establish- 
ments of the Government in the purchase of materials covered by it. 


CONTENTS. 

; Page 
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ee ener eMarmindtion (iy)... fa ls2iitce . nubs they olay ua. paadeeers 2 
SE a a as! abcess OP gic OP. cn tes tbo ie 6 


1. GENERAL. 


The varnish shall be suitable for general interior use, including 
both rubbed and unrubbed finish, exclusive of floors. It must be 
capable of easy application with a brush in the ordinary manner 
according to the rules of good standard practice, must flow out 
to a good level coat free from runs, sags, pits, or other defects, and 
dry with reasonable promptness to a hard, somewhat elastic glossy 
coating which can be rubbed in 48 hours or less. ‘The manufac- 
_ turer is given wide latitude in the selection of raw materials and 
processes of manufacture, so that he may produce a varnish of 
the highest quality. The varnish must meet the following 
requirements: 


APPEARANCE. 
63901 °—23 


Clear and transparent. 


2 Circular of the Bureau of Standards e 


CoLor.—Not darker than a solution of 3 g of potassium dichro- | 
mate in 100 ce of pure sulphuric acid, specific gravity 1.84. 

FLasu Pornt (cLosED-cup).—Not below 30° C. (85° F.). 

NoNnvVOLATILE MatTER.—Not less than 45 per cent by weight. 

Set to Toucu.—In not more than 4 hours. 

Dry Harp.—In not more than 24 hours. 

Dry to Rus.—In not more than 48 hours. 

TOUGHNESS.—Film on metal must stand rapid bending over a 
rod 3 mm (% inch) in diameter. 

Worxkinc PRopERTIES.—Must have good brushing, flowing, 
covering, leveling, and rubbing properties; and must show no 
impairment of luster or other defect when used where natural or 
illuminating gases aré burned or when subjected to air currents 
during the process of drying or application. 

Water RESISTANCE.—The dried film must stand application 
of cold water for not less than 18 hours without whitening or 
showing other visible defect. 


Note.—Deliveries will, in general, be sampled and tested, by the following methods, but the pur- 
chaser reserves the right to use any available information to ascertain whether the material meets the 


specification. 
2. SAMPLING. 


It is mutually agreed by buyer and seller that a single package 
out of each lot of not more than 1,000 packages shall be taken as 
representative of the whole. Whenever possible, an original un- 
opened container shall be sent to the laboratory, and when for 
any reason this is not done, the inspector shall thoroughly mix 
the contents of the container sampled, transfer not less than 1 
quart to a clean dry glass bottle or tin can which must be nearly 
filled with the sample, securely stoppered with a new clean cork 
or well-fitting cover, or cap, sealed, and distinctly labeled by the 
inspector. 

The inspector should take a duplicate from the container 
sampled to be held for check in case of dispute, and, when re- 
quested, should take a sample for the seller. 


3. LABORATORY EXAMINATION. 


The tin panels used in the following tests shall be cut from — 
bright tin plate weighing not more than 25 g nor less than 19 
g per square decimeter (0.51 to 0.39 pound per square foot). 
(Commercial No. 31 gage bright tin plate should weigh about 
0.44 pound per square foot. It is important that the tin plate 
used shall be within the limits set.) | | 


Specification for Intertor Varmsh 3 


(a) APPEARANCE.—Pour some of the thoroughly mixed sam- 
ple into a clear glass bottle or test tube and examine by trans- 
mitted light. The varnish must be clear and transparent. 

(b) CoLor.—Prepare a standard color solution by dissolving 
3 g of pure powdered potassium dichromate in 100 cc of pure 
concentrated sulphuric acid of specific gravity 1.84. Gentle. 
heat may be used if necessary to perfect the solution of the di- 
chromate. The standard color solution and a sample of the 
varnish to be tested shall be placed in clear, thin-walled glass 
tubes of the same diameter. The color comparison shall be 
made by placing the tubes close together and looking through 
them by transmitted light. The tubes used for this test should 
be 1.5 to 2.0 cm (5% to 18 inch) in diameter and shall be filled to 
a depth of at least 2.5 cm (1 inch). (Since the potassium di- 
chromate-sulphuric acid must be freshly made for this color 
comparison, it is frequently more convenient to compare samples 
with a permanently sealed tube of varnish which has previously 
been found to be slightly lighter in color than the standard solu- 
tion of 3 g dichromate in sulphuric acid. When samples are 
found to be darker than this standard tube of varnish, the di- 
chromate standard should be made up for final decision.) | 

(c) FLasH Pornt.—Determine with either the Tag or Elliott 
closed-cup tester. The former is preferred.’ 

(d) NonvVOLATILE MaTrer.—Place a portion of the sample in a 
stoppered bottle or weighing pipette. Weigh container and sam- 
ple. ‘Transfer about 1.5 g of the sample to a weighed flat-bot- 
tomed metal dish about 8 cm diameter (a friction-top can plug). 
Weigh container again and by difference calculate the exact weight 
of the portion of sample transferred to the weighed dish. Heat 
_ dish and contents in an oven maintained at 105 to 110° C. (221 to 
230° F.) for three hours. Cooland weigh. From the weight of the 
residue left in the dish and weight of the sample taken, calculate 
the percentage of nonvolatile residue. 

(ec) Dryinc TimE.—Pour the varnish on a clean glass or bright 
tin plate not less than 15 cm (6 inches) long and 1ocm (4 inches) 
wide. Place the plate in a nearly vertical position in a well- 
ventilated room but not in the direct rays of the sun. The tempera- 
ture of the room should be from 21 to 32°C. (7o to 90° F.). The 
film is tested at points not less than 2.5 cm (1 inch) from the edges 
of the film by touching lightly with the finger. The varnish is 


1 Directions for using the Tag tester may be found in A. S. T. M. Standards D 56-21, and directions for 
using the Elliott cup in Proceedings A. S. T. M., 1917, pt. 1, D. 414. 


4 . Crrcular of the Bureau of Standards. 


from carbon dioxide and other acid fumes. Wash the residue on 

the paper or in the crucible with hot neutral alcohol until free from 
soap. Dry the filter paper or crucible and residue at 100 to 105°C. 
for three hours, cool, and weigh the total matter insoluble in alco-. 

hol. (Since the percentage of the matter insoluble in alcohol is not 
required under this specification, time may be saved by omitting 
the drying and weighing and proceeding directly with the moist 
residue to the determination of matter insoluble in water (ae 

(2) FREE ALKALI oR Free Actp.—Titrate the filtrate from the 
above, using phenolphthalein as indicator, with standard acid or 
alkali solution, and calculate the alkalinity to sodium hydroxide 
(or potassium hydroxide) or acidity to oelic acid. | 

(3) Matrer INSOLUBLE IN WatTER.—Proceed as in the deter- 
mination of matter insoluble in alcohol. After filtering and 
thoroughly washing the residue, extract it with water at 60° C. 
and wash the filter thoroughly. (When the matter insoluble in 
water is all inorganic, boiling water may be used for the extraction 
and washing.) Dry the filter and residue at 100 to 105° C. for , 
three hours, cool, and weigh matter insoluble in water. The 
nature of this may be determined by further examination. ‘The 
insoluble matter should be siliceous. ‘The approximate amount of 
feldspar contained in the abrasive material of scouring soap 
(when such material is known to contain nothing but feldspar or 
quartz or a mixture of the two) may be determined by decom- 
posing about 0.5 g of the abrasive material with hydrofluoric 
acid, taking up the residue in water and hydrochloric acid and 
determining the Al,O,. This weight multiplied by 5.48 and 
divided by the weight of sample gives the approximate percentage 
of feldspar in the abrasive material. Feldspar may be identified 
and the relative amounts of feldspar and quartz roughly deter- 
mined by means of the petrographic microscope. 

(4) ALKALI AS ALKALINE SALTS (TOTAL AKLALINITY OF MATTER 
INSOLUBLE IN ALCOHOL).—Titrate the filtrate from the deter- 
mination of matter insoluble in water with standard acid, using 
methyl orange as indicator. Calculate alkalinity to sodium car- 
bonate (Na,CO,). 

(d) Steve Test.—Transfer a weighed sample of the insoluble 
siliceous material to a No. 100 sieve and carefully brush through. 
Weigh the amount passing through and calculate percentage. 
After weighing transfer to a No. 200 sieve and treat in the same 
manner. Weigh the amount passing through and calculate per- 
centage. i 


Specification for Interior Varnish 5 


from the top of the plate. Let panel stand in the same position 
for 20 minutes longer, then lay flat. An exaggerated condition of 
a dusty room shall be created by rubbing some cotton batting 
between the hands immediately over the panel. Let panel dry 
for a total of 48 hours in a well-ventilated room. If the comb 
marks show at this time, the varnish shall be rejected. If no 
comb marks show, the surface shall then be rubbed with pumice 
flour, water, and a felt pad with long, even, firm strokes back and 
forth in one or another direction, but not in circles, until every 
portion of the panel has been rubbed. Most of the pumice will 
then be removed from the pad and panel, and the varnish film 
given a ‘‘water rub” with the pad. 

A satisfactory rubbing varnish in the above test will yield a 
smooth, dull film even at those places where the dust particles 
have been encrusted in the film, and shall show no spots where 
the pumice has been ground into and become attached to the film, 
nor show any other evidence of gumming. No sweating shall 
occur anywhere on the film in 18 hours after rubbing. 

(2) Gas TEst.—A pparatus.—The necessary apparatus consists 
of a glass bell jar approximately 20 cm (8 inches) in diameter and 
30 cm (12 inches) in height, inside dimensions, having a ground- 
glass rim; a ground-glass base plate of suitable size: a small, 
kerosene glowlamp without chimney, or a small alcohol lamp 
filled with kerosene, using a round wick not over 6 mm (14 inch) 
in diameter and adjusted to give a flame 2 cm (4/, inch) in height. 
A wire or a light wooden frame is fitted inside the jar and provided 
with a support for holding a disk of tin plate 15 cm (6 inches) in 
diameter in a horizontal position 5 cm (2 inches) above the wick 
of the lamp. The frame must also be provided with several other 
supports above this disk for holding in a horizontal position the 
various varnished panels under test. The test panels consist of 
semicircular pieces of bright tin plate approximately 15 cm (6 
inches) in diameter.. 

The form and arrangement of the above apparatus is designed 
to provide an even distribution of the products of combustion 
over the test panels. 

Method.—First determine the normal time required for the 
varnish under examination to set to touch at room temperature. 
Divide this time by five to arrive at the different drying periods 
at which the varnish is to be tested in the gas tester. ‘Thus, if a 
varnish sets to touch in five hours, samples should be tested for 
resistance to gas at drying periods of one, two, three, and four 


6 Circular of the Bureau of Standards 


hours; it is needless to use the fifth or five-hour period for the 
above varnish, as a varnish which has set to touch is practically 
immune to injury from gas fumes. Similarly a varnish which 
sets to touch in one hour should be tested for resistance to gas at 
drying periods of 12, 24, 36, and 48 minutes. 

Example.—A varnish which sets to touch in five hours is tested 
as follows: 

First, clean two of the semicircular, bright, tin-plate panels 
carefully with benzol. Flow the varnish on one-half of panel 
No. 1 at, say, ro a, m., and allow to drain in a nearly vertical 
position at room temperature. At 11 a. m., flow the varnish on 
the other half of panel No. 1; allow to drain as before. At 12 m. 
varnish one-half of panel No. 2, and at 1 p. m. varnish the other 
half, as above. At 2 p. m. place the two panels close together in 
a horizontal position on the upper supports of the frame. Light 
the lamp and set it under the circular tin. Place the bell jar in 
position, centering it as nearly as possible, properly seated on the 
eround-glass plate. If the chamber is tight and lamp properly 
adjusted, the flame will be extinguished in about four minutes. 
After the panels have been in the chamber for half an hour, 
remove the bell jar and examine the varnished panels for gas 
effects. : 

he varnish on all four sections should remain bright and clear 
without trace of pitting, ‘‘crow’s footing,” frosting, or other 
defects. 

4, BASIS OF PURCHASE. 


Varnish shall be purchased by volume, the unit being a gallon 
of 231 cubic inches at 15.5° C. (60° F.). The volume may be deter- 
mined by measure, or, in case of large deliveries, it may be easier 
to determine the net weight and specific gravity at 15.5/15.5° ©. 
(60/60° F.) of the delivery. The weight per gallon in pounds can 
then be determined by multiplying the specific gravity by 8.33. 
The net weight in pounds divided by the weight per gallon gives 
the number of gallons. . | 


ADDITIONAL COPIES 
OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 
AT 
5 CENTS PER COPY 


V 


WASHINGTON : GOVERNMENT PRINTING OFFICE : 1922 


tal 


A Oe 


U. S. Gov't 
Standard 
Specification, 


No. 66. 
DEPARTMENT OF COMMERCE. 


BUREAU OF STANDARDS. 


George K. Burgess, Director. 


CIRCULAR OF THE BUREAU OF STANDARDS, NO. 146. 


[Issued September 25, 1923.] 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
WATER-RESISTING RED ENAMEL. 


FEDERAL SPECIFICATIONS BOARD. 
STANDARD SPECIFICATION NO. 66. 


This specification was officially adopted by the Federal Specifications Board 
on September 1, 1923, for the use of the Departments and Independent Estab- 
lishments of the Government in the purchase of water-resisting red enamei. 


CONTENTS. 
Page 
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1. GENERAL. 


The material desired under this specification is an extremely 
durable, highest quality red enamel, suitable primarily for outside 
use. It should be made by grinding pure high color strength 
toluidine red toner (metanitro-paratoluidine-azo-betanaphthol), 
free from any base or substratum, with the very best water- 
resisting long oil spar varnish. The color and hiding power 
when specified shall be equal to those of a sample mutually 
agreed upon by buyer and seller. It must meet the following 
requirements: 

WEIGHT PER GALLON.—Not less than 7!% pounds. 

PIGMENT.—Not less than 6 per cent by weight; pigment to be 
composed entirely of pure high color strength toluidine red 
toner, free from any other organic coloring matter, base, or 


substratum. 
61692 °—23 


2 Circular of the Bureau of Standards. 


CoARSE PARTICLES AND ‘‘SKINS” (total residue retained on No. 
325 sieve).—Not more than 0.5 per cent. 

NoNVOLATILE MaTtER.—Not less than 60 per cent by welghiee 

Set to Toucu.—In not more than 18 hours. 

Dry Harp AND ToucH.—In not more than 48 hours. 

WorKING PROPERTIBS.—Enamel must have good brushing, 
flowing, covering, and leveling properties and must not cake in 
the container. 

WATER RESISTANCE.—Dried film must withstand cold water for 
18 hours and boiling water for 15 minutes without whitening, 
dulling, or change in color. 

TOUGHNESS.—Enamel must pass a 50 per cent Kauri reduction 
teStat eas oR ae 

Deliveries will, in general, be sampled and tested by the following ~ 
methods, but the purchaser ‘reserves the right to use any addttronal 
available information to ascertain whether the material meets the 
specification. 

2. SAMPLING. 

It is mutually agreed by buyer and seller that a singh package 
out of each lot of not more than 1,000 packages be taken as repre- 
sentative of the whole. Whenever possible, an original unopened 
container shall be sent to the laboratory, and when for any rea- 
son this is not done the inspector shall thoroughly mix the con- 
tents of the container sampled, transfer not less than 1 quart 
to a clean, dry glass bottle or tin can, which must be nearly filled 
with the sample, securely stoppered with a new, clean cork or well- 
fitting cover or cap, sealed and distinctly labeled by the inspector. 
The inspector should take a duplicate from the container sampled 
to be held for check in case of dispute, and, when requested, 
should take a sample for the seller. 


3. LABORATORY EXAMINATION. 


The tin panels used in the following tests shall all be cut from — 
bright tin plate weighing not more than 25 nor less than 19 g per 
square decimeter (0.51 to 0.39 pound per square foot). (Com- 
mercial No. 31 gauge bright tin plate should weigh about 0.44 
pound per square foot. It is important that the tin plate used 
shall be within the limits set.) The panels shall be about 7.5 by 
13 cm (3 by 5 inches) and must be thoroughly" cleaned with 
benzol immediately before using. 

(a) CAKING IN CONTAINER AND WORKING PROPERTIES.—When 
an original package is received in the laboratory, it shall be 


Specification for Water-Resisting Red Enamel. 3 


weighed, opened, and stirred with a stiff spatula or paddle. The 
enamel must be no more difficult to break up than a normal good 
grade of enamel paint. The enamel shall finally be thoroughly 
mixed, removed from the container, and the container wiped 
clean and weighed. This weight subtracted from the weight of 
the original package gives the net weight of the contents. Apply 
some of the thoroughly mixed enamel, both by brushing and 
flowing, to clean glass plates. It should work easily under the 
brush. Dry both plates in a nearly vertical position. They 
should both dry without streaking, separating, or showing brush 
marks. A portion of thoroughly mixed enamél shall be placed 
in a clean container and the portions for the remaining tests 
promptly weighed out. 

(b) CoLOR AND HipiInc PowEr.—Place some of the enamel on a 
clean, clear glass plate. Place some of the standard agreed upon 
beside the sample on the plate, turn the glass over, and compare 
the colors by transmitted and reflected light. 

(c) WEIGHT PER GALLON.—Weigh a clean, dry, 100 ce gradu- 
ated flask. Fill to the mark with the thoroughly mixed enamel and 
weigh again. ‘The increase in weight expressed in grams, divided 
by 100, gives the specific gravity, which, multiplied by 8.33, 
gives the weight in pounds per gallon. 

(d) COARSE PARTICLES AND SKINS.—Dry in an oven at 105 to 
110° C. a No. 325 sieve, cool, and weigh accurately. Weigh 
accurately about 50 g of the enamel, add 100 cc of kerosene, mix 
thoroughly, and wash with kerosene through the sieve, breaking 
up all lumps, but not grinding. After washing with kerosene 
until all but the particles too coarse to pass the sieve have been 
washed through wash all kerosene from the sieve with ether or 
petroleum ether, heat the sieve for one hour at 105 to 110° C., 
cool, and weigh. 

(e) PIGMENT.—Qualitative examination. Poe about 1 g of the 
thoroughly stirred enamel, previously strained through a No. 200 
SIEVE: IM)..a )50..cC baler Add about 4o ce of chloroform 
(U.S. P.) and warm on the steath bath, stirring with a glass rod. 
A clear orange-red solution should result in a few minutes. Take 
another portion of the enamel and spread it with a spatula on a 
smooth, white surface, such as a piece of milk glass. Touch a few 
drops of alcoholic sodium hydroxide solution to the center of the 
film and rub well witha glass spatula. There should be no change 
in color.! 


_—_— 


1 The presence of para nitraniline red is indicated by a violet color. 


4 Circular of the Bureau of Standards. 


Quantitative. determination. Weigh 1 g (+ 10 mg) of the 
enamel and 6 g (+ 10 mg) of pure zinc oxide, place on a large 
glass plate, add 2 cc of linseed oil and rub up with a flat-bottomed 
glass pestle or muller, grinding with a circular motion 50 times. 
Gather up with a sharp-edge spatula and grind out twice more 
in like manner, giving the pestle a uniform pressure. Next 
weigh to + 1 mg an amount of pure high color strength toluidine 
red toner equal to 6 per cent of the weight of enamel taken, 
add 4 drops of linseed oil and rub up with the glass pestle. 
Then add 6 g of pure zinc oxide and 2 cc of linseed oil and treat 
in exactly the same manner as described above. Transfer por- 
tions of each paste to a clean microscope slide quite close together, 
and then draw a palette knife across both samples, so as to make 
them meet in a line. Compare the tints as shown on both sides 
of the glass. The color of the sample tested shall be not less 
than that of the selected standard, and the tone shall be not 
materially different from it. 

(7) NONVOLATILE MATTER.—Place a portion of the sample in a 
stoppered bottle or weighing pipette. Weigh container and sam- 
ple. Transfer about 1.5 g of the sample to a weighed flat-bot- 
tomed metal dish about 8 cm in diameter (a friction-top can plug). 
Weigh container again and by difference calculate the exact weight 
of the portion of sample transferred to the weighed dish. Heat 
_ dish and contents in an oven maintained at 105 to 110° C. (221 to 
230° F.) for three hours. Cool and weigh. From the weight of 
the residue left in the dish and weight of the sample taken calcu- 
late the percentage of nonvolatile residue. 

(g) Dry1inc Time.—Pour the enamel on one of the tin panels 
described above. Place the panel in a nearly vertical position in 
a well-ventilated room, but not in the direct rays of the sun. The 
atmosphere of this room must be free from products of combus- 
tion or laboratory fumes. The temperature of the room should 
be from 21 to 32°C. (7o to 90° F.). The film is tested at points 
not less than 2.5 cm (1 inch) from the edges of the film by touch- 
ing lightly with the finger. The enamel is considered to have set to 
touch when gentle pressure of the finger shows a tacky condition, 
but none of the enamel adheres to the finger. The enamel is con- 
sidered to have dried hard when the pressure that can be exerted 
between the thumb and finger does not move the film or leave a 
mark which remains noticeable after the spot is lightly polished. 
If rapid, light rubbing breaks the surface, the sample is considered 
not to have satisfactorily dried hard. In case the test shows time 
of setting to touch or drying hard more than 18 and 48 hours, 


Specification for Water-Resisting Red Enamel. 5 


respectively, two additional tests shall be run on different days, 
and if the enamel does not meet the above drying and hardening 
requirements on both of these additional tests it shall be con- 
sidered unsatisfactory. In cases where different laboratories fail 
to agree on the drying test, due to different atmospheric condi- 
tions, and umpire tests are necessary, such tests shall be made in 
a well-ventilated room maintained at a temperature of 70° F. and 
relative humidity of 65 per cent saturation. 

(h) WATER RESISTANCE.—Pour the enamel on two of the tin 
panels described above and allow to dry under the conditions 
described in paragraph (g) for 48 hours. Place one of these panels 
in a beaker containing about 2.5 inches of distilled water at room 
temperature (immersing the end of the panel which was upper- 
most during the drying period) and leave in water for 18 hours. 
The enamel shall show no whitening and no more than very slight 
dulling either when observed immediately after removing from the 
water or after drying for 2 hours. Place the other panel in a 
beaker containing about 2.5 inches of boiling distilled water (im- 
_mersing the end of the panel which was uppermost during the 
drying period) and allow to remain in the boiling water for 15 
minutes. The enamel shall show no whitening, no more than a 
very slight dulling, and no material change in color, either when 
observed immediately after removing from the water or after 
drying for 2 hours. 

(2) TOUGHNESS.—The toughness of the enamel is determined 
by the Kauri reduction test, as follows: By proportioriately reduc- 
ing its toughness by the addition of a standard solution of “‘run- 
Kauri” gum in pure spirits of turpentine. 

(1) Preparation of the “run Kawur.’’—Arrange a distillation 
flask, water-cooled condenser, and a tared receiver on a balance. 
Place in the flask about one-third of its volumetric capacity 
of clear, bright hard pieces of Kauri gum broken to pea size. 
Carefully melt and distil until 25 per cent, by weight, of the gum 
taken is collected in the tared receiver. (At the end of the distil- 
lation the thermometer in the distillation flask with the bulb at 
the level of the discharging point of the flask should register about 
316° C. (600° F.).) Pour the residue into a clean pan, and when 
cold break up into small pieces. 

(2) Preparation of standard “run-Kaurv’”’ solutton.—Place a 
quantity of the small broken pieces of run-Kauri, together with 
twice its weight of freshly redistilled spirits of turpentine, using 
only that portion distilling over between 153 and 170° C. (308 
and 338° F.) in a carefully tared beaker. Dissolve by heating 


6 Circular of the Bureau of Standards. 


to a temperature of about 149° C. (300° F.) and bring back to 
correct weight when cold by the addition of the amount of redis- 
tilled spirits of turpentine necessary to replace the loss by evapora- 
tion during the dissolving of the gum. 

(3) Reduction of the enamel.—Having carefully determined the 
nonvolatile content of the enamel according to the method under 
paragraph (f) of this specification, take 100 g of the enamel and 
add to it an amount of the standard run-Kauri solution equiva- 
lent to 50 per cent, by weight, of the nonvolatile matter in the 
enamel. Mix the enamel-and the solution thoroughly. 

(4) Application of the enamel.—Flow a coat of the enamel thus 
reduced on one of the tin panels described above and let stand 
in a nearly vertical position at room temperature for one hour. 
Next place the panel in a horizontal position in a properly venti- 
lated oven and bake for five hours at 95 to 100° C. Remove the 
panel from the oven and allow to cool at room temper ears prefer- 
ably 24° C. (75° F.) for one hour. 

(5) Bending the panel.—Place the panel with the enameled side 
uppermost over a 3-mm (% inch) rod, held firmly by suitable 
supports, at a point equally distant from the top and bottom 
edges of the panel and bend the panel double rapidly. The enamel 
must show no cracking whatsoever at the point of bending. For 
accurate results the bending of the panel should always be done 
at 24° C. (75° F.), for a lowering of the temperature will lower the 
percentage of reduction that the enamel will stand without cracking, 
while an increase in the temperature increases the percentage of 
reduction that the enamel will stand. 


4. BASIS OF PURCHASE. 


Enamel shall be purchased by volume, the unit being a gallon 
of 231 cubic inches at 15.5° C. (60° F.). The volume may be 
determined by measure or, in case of large deliveries, it may be 
easier to determine the net weight and specific gravity at 15.5/15.5° 
ee (60/60° F.) of the delivery. The weight per gallon in pounds 
can then be determined by multiplying the specific gravity by 8.33. 
The net weight in pounds divided by the weight per gallon ee 
the number of gallons. 


ADDITIONAL COPIES 
OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFIC® 
WASHINGTON, D. C. 
AT 
5 CENTS PER COPY 


PURCHASER AGREES NOT TO RESELL OR DISTRIBUTE THIS 
COPY FOR PROFIT.—PUB. RES. 57, APPROVED MAY II, 1923. 


4 


~, 


« 


U. S. Gov't 
Standard 
Specification, 


No. 67. 
DEPARTMENT OF COMMERCE. 


BUREAU OF STANDARDS. 


George K. Burgess, Director. 


CIRCULAR OF THE BUREAU OF STANDARDS NO. 147. 
(Issued September 19, 1923.) 


UNITED STATES GOVERNMENT SPECIFICATION FOR 
GLOSS INTERIOR LITHOPONE PAINT, WHITE AND 
LIGHT TINTS. 


FEDERAL SPECIFICATIONS BOARD. 
STANDARD SPECIFICATION NO. 67. 


This specification was officially adopted by the Federal Specifications Board 
on September |, 1923, for the use of the Departments and Independent Establish- 
ments of the Government in the purchase of gloss interior lithopone paint, white 
and light tints. 


CONTENTS. 


Page. 

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IRE gs eck oa oe rads ccs tee hewedeaecuesaue 2 

EE rR alls ae es ee OL oe ne ee ee 3 

RR Tg ec a rises S Sistc vip ene Wide Gu ajerhelnre mip vsie' dw «aid a abe 6 

a ies ce ceases tase eke cbse eg es seer de ss aes 8 
1. GENERAL. 


This specification covers ready-mixed lithopone paints, fre- 
quently known as gloss mill white, in white and a variety of light 
tints. Paints under this specification are not intended for out- 
side exposure. ‘They shall dry to gloss opaque coats that will 
adhere well to wood, metal, and plaster, stand washing with soap 
and water, and show no material change in color on exposure to 
light or material yellowing when kept in the dark. 

‘The paint shall be purchased by volume (231 cubic inches to 
the gallon). 


61693°—23 


2 Circular of the Bureau of Standards. 


(a) P1cMENT.—The pigment shall consist of : 


Maximum.) Minimum. 


Per cent. | Per cent. 
Li OPOMe be wee ong& jcc vis wo's coh wcteleleie'u'e wie alae 8. dieihol ale hela a tain ise, o ara 9m alps} a: bvale Wate opty te ne rnana ana 65 


ZINC OFIGS, co cis <x sivie ales Siaeu clad ccmula op pine ara pioisioie ewes ccn sidik elu laie «= igitealave aucis etntere a Orta mn nes 20 
Tinting and extending pigments. 0.05.85 205/02... 54.5 sh cok: cas vom Gabe ch + gue cen ee $. 0 liwecsueesteon 
Material soluble in: Water. oot soe conc coe ene chelate bop als se bss a mialeipeelcrecamtnyercey ena O58 ee omen 


ee ene eA ed ns eee oe ee eee eee sa 
1 The lithopone used must contain not less than 26 per cent of zinc sulphide and must not darken on 
exposure. 


In no case shall the sum of zinc oxide and lithopone be less 
than 95 per cent. 

(b) Liourw.—The liquid portion of the patht shall consist of 
treated drying oils or varnish, or a mixture thereof, and turpen- 
tine or volatile minera' spirits, or a mixture thereof, in such pro- 
portions as to insure not less than 60 per cent of nonvolatile 
vehicle. ‘The nonvolatile vehicle shall dry to a tough and elastic 
film. ; 

(c) Parnt.—The paint shall be well ground, shall not settle 
badly, cake, or thicken in the container, shall be readily broken 
up with a paddle to a smooth, uniform paint of brushing consist- 
ency, and shall dry within 24 hours to a varnish gloss finish with- 
out streaking, running, or sagging, and free from laps and brush 
marks. ‘The color and hiding power when specified shall be equal 
to those of a sample mutually agreed upon by buyer and seller, 
After drying for not less than five days marks made on the painted 
surface with a soft lead pencil (No. 2 Mogul) shall be easily re- 
moved by washing with soap and warm water without appre- 
ciably marring the paint surface. The weight per gallon shall be 
not less than 1244 pounds. ‘The paint shall consist of: 


Maximum.| Minimum. 


Percent. | Per cent. 
6 50 


PUPMONE 0 5 eso ess ks oo 6 eal wie Saws male age Se os La ata reat wis Nh: 9; 2. agai 6 his wate 0 
Liquid ( (POE at least 60 per cent nonvolatile matter)..................0eceee 50 
CL) eae ae EL De yon NL bie ee a RANE AREER IMS MRIS La ia enesn es 
rare particles and “‘skins’’ (total residue retained on No. 325 screen based on 
PIFMENE) ha os cow eecle a ee a AUIS ae ae » Le NMED. Sete Wee Fv erin OS Aegean 


Deliveries will, in general, be sampled and tested by the following 
methods, but the purchaser reserves the right to use any additional 
avatlable information to ascertain whether the material meets the 
mori ice aie 

2. SAMPLING. 

It is Se See agreed by buyer and seller that a single package 
out of each lot of not more than 1,000 packages shall be taken as 
representative of the whole. Whenever possible, an original 


Specification jor Gloss Intertor Lithopone Paint. 3 


unopened container shall be sent to the laboratory, and when this 
is for any reason not done the inspector shall determine by thorough 
testing with a paddle or spatula whether the material meets the 
requirement regarding caking in the container. He shall then 
thoroughly mix the contents of the container and draw a sample 
of not less than 5 pounds. This sample shall be placed in a clean, 
dry metal or glass container, which it must nearly fill. The con- 
tainer shall be closed with a tight cover, sealed, marked, and sent 
to the laboratory for test with the inspector’s report on caking. 
_ When requested, a duplicate sample may be taken from the 
same package and delivered to the seller, and the inspector may 
take a third sample to hold for test in case of dispute. 


3. LABORATORY EXAMINATION. 


(a) CAKING IN CONTAINER.—When an original package is 
received in the laboratory, it shall be weighed, opened, and 
stirred with a stiff spatula or paddle. The paint must be no more 
difficult to mix to a uniform consistency than a good grade of 
gloss mill white. The paint shall finally be thoroughly mixed, 
removed from the container, and the container wiped clean and 
weighed. This weight subtracted from the weight of the original 
package gives the net weight of the contents. A portion of the 
thoroughly mixed paint shall be placed in a clean container and 
portions for the remaining tests promptly weighed out.. 

(6) CoLor.—Place some of the paint on a clean, clear glass 
plate. Place some of the standard agreed upon beside the sample 
on the plate, turn the glass over, and compare the colors. 

(c) WEIGHT PER GALLON.—Weigh a clean, dry, roo ce grad- 
uated flask. Fill to the mark with the thoroughly mixed paint 
and weigh again. ‘The increase in weight expressed in grams, 
divided by 100, gives the specific gravity, which, multiplied by 
8.33, gives the weight in pounds per gallon. 

(d) BRUSHING PROPERTIES, TIME OF DRYING, AND RESISTANCE 
TO WASHING.—Brush the well-mixed paint on a suitable panel, 
which may be ground glass, steel, or well-filled wood. Note 
whether the paint works satisfactorily under the brush. Place 
the panel in a vertical position in a well-ventilated room and let 
it stand for 24 hours. The paint should be dry and free from 
streaks. Let the panel stand for five days, then make marks on 
it with a soft lead pencil (No. 2 Mogul) and wash these marks off 
with warm (75° C.) distilled water and white floating soap, using 


4 Circular of the Bureau of Standards. 


a sponge or soft rag. The marks must be removed by this treat- 
ment without appreciably marring the paint film. 

Flow a portion of the paint on a clean glass plate. Let dry ina 
nearly vertical position at room temperature (65 to 100° F.). The 
film shall show no streaking or separation within a distance of 
4 inches from the top. 

(ec) FastNEss TO Licut.—Apply a sufficient number of coats 
of the paint to a ground-glass plate to completely hide the sur- 
face, cover half of this painted surface with opaque black paper, 
and expose indoors in a well-lighted room for five days. Remove 
the black paper and examine the surface. The exposed portion 
should be no darker than the portion protected by the black 
paper. 

(7) YELLOwinc.—Apply a sufficient number of coats of the 
paint to two ground-glass plates to completely hide the surface; 
after applying the last coat let dry in a well-lighted room for 
five days. Place one of the plates in a dark room or cabinet * 
with a warm, very humid atmosphere, for 96 hours. Remove 
from cabinet and compare with the plate that has been kept in 
a light room, ‘The plate kept in the dark shall be only slightly 
yellower than the plate kept in the light. There shall be no 
greater difference in color of the two plates than there will be 
with similar plates coated with the best grade of paint of this 
general nature. 

(g) WATER.—Mix 100 g of the paint in a 300 cc flask with 75 
ce of toluol. Connect with a condenser and distil until about 50 
cc of distillate has been collected in a graduate. The temperature 
in the flask should be then about 105 to 110° C. ‘The number of 
cubic centimeters of water collecting under the toluol in the 
receiver is the percentage of water in the paint. | 

(h) VOLATILE THINNER.—Weigh accurately from 3 to 5 g 
of the paint into a tared flat-bottomed dish about 5 cm in diam- 
eter, spreading the paint over the bottom. Heat at 105 to 110° 
C. for one hour, cool, and weigh. Calculate the loss in weight as 
percentage of water and volatile thinner, subtract from this the 
percentage of water (3, g), and report the remainder as volatile 
thinner. 

(1) PERCENTAGE OF PIGMENT.—Weigh accurately about 15 g 
of the paint into a weighed centrifuge tube. Add 20 to 30 cc 
of ‘“‘extraction mixture” (see Reagents), mix thoroughly with a 


‘A convenient cabinet for this test is described in Circular No. 152, Educational Bureau, Scientific 
Section, Paint Manufacturers’ Association of the United States. 


Specification for Gloss Interior Lithopone Paint. 5 


glass rod, wash the rod with more of the extraction mixture, and 
add sufficient of the reagent to make a total of 60 cc in the tube. 
Place the tube in the container of a centrifuge, surround with 
water, and counterbalance the container of the opposite arm with 
a similar tube or a tube with water. Whirl at a moderate speed 
until well settled. Decant the clear supernatant liquid. Repeat 
the extraction twice with 40 cc of extraction mixture and once 
with 40 cc of ether. After drawing off the ether set the tube in a 
beaker of water at about 80° C. or on top of a warm oven for 10 
minutes, then in an oven at 110 to 115° C. for two hours. Cool, 
weigh, and calculate the percentage of pigment. Grind the pig- 
ment to a fine powder, pass through a No. 80 sieve to remove any 
skins, and preserve in a stoppered bottle. Preserve the extracted 
vehicle for 3 (&). 

(7) PERCENTAGE OF NONVOLATILE VEHICLE.—Add together 
the percentages of water (3, g), of volatile thinner (3, 2), and of 
pigment (3, 7), and subtract the sum from too. ‘The remainder 
is the percentage of nonvolatile vehicle. 

(k) NaTURE OF NONVOLATILE VEHICLE.—Evaporate the ex- 
tracted vehicle and extraction mixture from 3 (¢) to about 5 ce. 
Thoroughly clean with benzol a piece of bright sheet iron, tin 
plate, or terneplate. Spread a portion of the concentrated 
extracted vehicle on the sheet of metal, allow to dry for 30 minutes 
at room temperature in a vertical position, bake for three hours 
at 100 to 110°C. (212 to 221° F.), remove from the oven, and keep 
at room temperature for three days. Place the panel with the 
coated side uppermost over a 3 mm (!-inch) rod, held firmly by | 
suitable supports, at a point equally distant from the top and 
bottom edges of the panel and bend double rapidly. The dried 
vehicle must show no cracking whatever at the point of bending. 
Test the film with a knife blade at a place not less than 2.5 cm 
(rx inch) from the edge. The film should be tough and elastic. 
If it powders, or if particles fly under the test, it will be considered 
brittle, which will be cause for rejection. The film must also 
stand light, vigorous rubbing with the finger without powdering 
or disintegrating. 

(1) COARSE PARTICLES AND SKINS.—Dry in an oven at 105 to 
110° C. a No. 325 sieve, cool, and weigh accurately. Weigh an 
amount of paint containing 10 g of pigment (see 3, 2), add so ce 
of kerosene, mix thoroughly, and wash with kerosene through 
the sieve, breaking up all lumps, but not grinding. After washing 


6 Circular of the Bureau of Standards. 


with kerosene until all but the particles too coarse to pass the sieve 
have been washed through wash all kerosene from the sieve with 
ether or petroleum ether, heat the sieve for one hour at 105 to 
110° C., cool, and weigh. 


4. ANALYSIS OF PIGMENT. 


Use the pigment extracted in 3 (7). . 

(2) QUALITATIVE ANALYsIS.—Make qualitative analysis, fol- 
lowing ordinary methods. 

(b) MarreR SOLUBLE IN WaTER.—Transfer 2.5 g of the pig- 
ment to a graduated 250 cc flask, add 100 cc of water, boil for five 
minutes, cool, fill to mark with water, mix, and allow to settle. 
Pour the supernatant liquid through a dry filter paper and dis- 
card the first 20 cc. ‘Then evaporate 100 cc of the clear filtrate 
to dryness in a weighed dish, heat for one hour at 105 to 110° C., 
cool, and weigh. 

(c) BARtuM SULPHATE AND SILICKOUS MATERIAL.—Transfer 1 
g of pigment to a porcelain casserole or dish, moisten with a few 
drops of alcohol, add 4o cc of hydrochloric acid (1.1 specific 
gravity), cover, and boil to expel hydrogen sulphide. Remove the 
cover and evaporate to dryness on the steam bath, moisten with 
hydrochloric acid, dilute with water, filter through paper, and 
wash with dilute hydrochloric acid and then with hot water until 
the washings are free from zinc and chlorine. Ignite and weigh 
the residue, which will be barium sulphate and siliceous material. 

Mix the ignited residue with about 10 times its weight of anhy- 
drous sodium carbonate (grind the mixture in an agate mortar, if 
necessary), fuse the mixture in a covered platinum crucible, 
heating about one hour. Let cool, place the crucible and cover in 
a 250 cc beaker, add about 100 cc of water, and heat until the melt 
is disintegrated. Filter on paper (leaving the crucible and cover 
in the beaker) and wash the beaker and filter thoroughly with 
hot water to remove soluble sulphates. Place the beaker con- 
taining the crucible and cover under the funnel, pierce the filter 
with glass rod, and wash the carbonate residue into the beaker 
by means of a jet of hot water. Wash the paper with hot, dilute 
hydrochloric acid (1:1) and then with hot water. If the car- 
bonate residue is not completely dissolved, add sufficient dilute 
hydrochloric acid to effect solution and remove the crucible and 
cover, washing them with a jet of water. Heat the solution to 
boiling and add 10 to 15 ce of dilute sulphuric acid and continue 
the boiling for 10 or 15 minutes longer. Let the precipitate 


Specification for Gloss Interior Lithopone Paint. 7 


settle, filter on a weighed Gooch crucible, wash with hot water, 
ignite, cool, and weigh as BaSO,. Subtract from the result of the 
previous determination to obtain the siliceous material. 

(d) Tora, ZINC CALCULATED AS ZINC OxIpE.—With material 
containing no interfering elements (iron, for example) weigh 
accurately about 1 g of pigment, transfer to a 400 cc beaker, 
moisten with alcohol, add 30 cc of hydrochloric acid (1:2), boil 
for two to three minutes, add 200 cc of water and a small piece of 
litmus paper; add strong ammonia until slightly alkaline, render 
just acid with hydrochloric acid, then add 3 cc of strong hydro- 
chloric acid, heat nearly to boiling, and titrate with standard 
ferrocyanide as in standardizing that solution (see Reagents). 
Calculate total zinc as zinc oxide. 

When iron or other interfering elements are present (see 4, a), 
take the filtrate containing the zinc from 4 (c), add a slight excess 
of bromine water and 2 g of ammonium chloride, heat to nearly 
boiling, add an excess of ammonia, heat for about two minutes, 
filter, dissolve the precipitate in hydrochloric acid, add 2 g of 
ammonium chloride, and reprecipitate with ammonia as above. 
Filter, wash the precipitate with hot 2 per cent ammonium- 
chloride solution, unite the two filtrates, and determine zinc as 


above. 7 
(e) ZINC OxIDE.—Weigh accurately 2.5 g of pigment, transfer 


to a 250 cc graduated flask, moisten with a few drops of alcohol, 
add about 200 cc of 1 to 3 per cent acetic acid, shake vigorously, 
and let stand for 30 minutes, shaking once very five minutes. Fill 
to the mark with 1 to 3 per cent acetic acid, mix, filter through a 
dry paper, discard the first 25 cc, and determine zinc in 100 cc of 
the filtrate (corresponding to 1 g) as in 4 (d). Calculate the 
percentage of zinc oxide. 

({) CALCULATIONS.—Subtract the percentage of zinc oxide (4, 
e) from the percentage of total zinc as zinc oxide (4, d) and multi- 
ply the remainder by 1.2 to convert to percentage of zinc sulphide. 
In case the percentage of barium sulphate (4, c) is not more than 
2.86 times as great as the percentage of zinc sulphide, add the two 
together and call the sum the percentage of lithopone. If the 
percentage of barium sulphate is greater than this amount, take 
2.86 times the percentage of zinc sulphide as the percentage of 
barium sulphate to be included in the percentage of lithopone and 
include the remainder in the percentage of tinting and extending 
pigments. Subtract the sum of the percentages of zinc oxide 


8 Circular of the Bureau of Standards. 


(4, e), lithopone, and matter soluble in water (4, b)from 100. Call 
the remainder percentage of tinting and extending pigments. 


5. REAGENTS. 


(a) EXTRACTION MIXTURE.— 

| 10 volumes ether (ethyl ether). 
6 volumes benzol. 
4 volumes methyl] alcohol. 
1 volume acetone. 

(b) ONE To THREE PER Centr Acetic Acip.—Dilute 20 cc of 
glacial acetic acid to 1,000 cc with distilled water. 

(c) UraNyL INDICATOR FOR ZINC TITRATION.—A 5 per cent 
solution of uranyl nitrate in water or a 5 per cent solution of 
uranyl acetate in water made slightly acid with acetic acid. 

(d) STANDARD POTASSIUM FERROCYANIDE.—Dissolve 22 g of the 
pure salt in water and dilute to1,000cce. To standardize, transfer 
about 0.2 g (accurately weighed) of pure metallic zinc or freshly 
ignited pure zinc oxide to a 400 cc beaker. Dissolve in 10 ce of 
hydrochloric acid and zoccofwater. Drop inasmall piece of litmus 
paper, add ammonium hydroxide until slightly alkaline, then add 
hydrochloric acid until just acid, and then 3 cc of strong hydro- 
chloric acid. Dilute to about 250 cc with hot water and heat 
nearly to boiling. Run in the ferrocyanide solution slowly from a 
burette, with constant stirring until a drop tested on a white 
porcelain plate with a drop of the uranyl indicator shows a brown 
tinge after standing one minute. A blank should be run with the 
same amounts of reagents and water as in the standardization. 
The amount of ferrocyanide solution required for the blank should 
be subtracted from the amount used in standardization and in 
titration of the sample. The standardization must be made 
under the same conditions of temperature, volume, and acidity as 
obtain when the sample is titrated. 


ADDITIONAL COPIES 


OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 


AT 
5 CENTS PER COPY 


PURCHASER AGREES NOT TO RESELL OR DISTRIBUTE THIS 
COPY FOR PROFIT.—PUB. RES. 57, APPROVED MAY II, 1922 


V 


U.S. Gov't 
Standard 
Speciéication, 


No. 115. 


DEPARTMENT OF COMMERCE. > 
BUREAU OF STANDARDS. 


George K. Burgess, Director. 


CIRCULAR OF THE BUREAU OF STANDARDS, No. 163. 
| [February 20, 1924.] 


UNITED STATES GOVERNMENT SPECIF ICATION FOR 
‘TITANIUM PIGMENT, DRY AND PASTE. 


FEDERAL SPECIFICATIONS BOARD. 
STANDARD SPECIFICATION No. 115. 


This specification was officially adopted by the Federal Specifications Board 
on February 20, 1924, for the use of the Departments and Independent Estab- 
lishments of the Government in the purchase of titanium pigment, dry and paste. 


CONTENTS. 
Page 
EE Als ie us 7 Feet oe Moke, a, ee ee 1 
peerrmrtrgr Tex cae td, S MIL BIS, TO bad SOFT BR ds sla aide 2 
3. Laboratory examination, dry pigment.............0.0/ 006.002.0000 22, 3 
4. Laboratory examination, PSC. - ueneaten ide «oe d... Seoeeimer ll. seer a. 6 
CUE ere ee A one he ae ORE, ae 9 
1. GENERAL. 


Titanium pigment may be ordered in the form of dry pigment or 
paste ground in linseed oil. The material shall be purchased by 
net weight. 

(2) Dry PicmMENT.—The pigment shall be 25 per cent titanium 
oxide precipitated upon and coalesced with 75 per cent of blanc 
fixe (precipitated barium sulphate). It shall be thoroughly 
washed, shall be free from adulterants, and shall meet the fol- 
lowing requirements. 

Color—Color strength.—When specified, the color and color 
strength shall be equal to that of a sample mutually agreed upon 
by buye and seller. 


84628°—24 


2 Circular of the Bureau of Standards 


i- | Marxi- 


Min 
mum. mum. 


Per cent. | Per cent. 

Coarse particles retdined on IN0..325 SeV@. 0.2 occ cdi ot oe es eeies ssa veins 0 oiedciesieisien oiininwem .0 

Titanium oxide (TiOds). . decay coms aide ep turn oe8 terete + de ts Spies coh ab aia re 24. OF sc uclaes Soe 

Total impurities, including moisture... ecu kk odeacds doe sdeeccbodece bacnbe tee analy at eta maam 1.0 
The remainder shall be barium culghabe. 


(b) Past#.—The paste shall be made by thoroughly grinding 
the above-described pigment with pure, raw, or refined linseed oil. 

The paste as received shall not be caked in the container and 
shall break up readily in oil to form a smooth paint of brushing 
consistency. The paste shall consist of: 


Mini- Maxi- 
mun, mum, 


Per cent. | Per cent. 


Pigtiont 2065 os naccc hws cise Gaui svboew ohisaewines Bes male els hs aimcep es cate ieee etn 80.0 85.0 

Linseedl ollie os occ cei ceca ons Swe oe Wnt Ciba gle wie wlan iw mine's eie ele ee eae ea 15.0 20. 0 
Moisture and other volatile matterec: <0. s A 7. voc ee ne. adn agen sob secek sek eae eb als eee eins ot 
Coarse particles and ** skins ” (total residue retained on No. 325 sieve, based on pig- is 


ment) 2 


Deliveries will, in general, be sampled and tested by the following 
methods, but the purchaser reserves the right to use any additional 
available information to ascertain whether the materval meets the 
specification. | 

2. SAMPLING. 

It is mutually agreed by buyer and seller that a single package 
out of each lot of not more than 1,000 packages be taken as repre- 
sentative of the whole. 

(a) Dry Picment.—The package is to be opened by the 
inspector and a sample of not less than 5 pounds taken at random 
from the contents and sent to the laboratory for test. 

(b) Paste.—Whenever possible, an original unopened con- 
tainer shall be sent to the laboratory; and when this is for any 
reason not done the inspector shall determine by thoroughly 
testing with a paddle or spatula whether the material meets the 
requirement regarding not caking in the container. (See 4 (@).) 
After assuring himself that the paste is not caked in the can, the 
inspector shall draw a sample of not less than 5 pounds of the 
thoroughly mixed paste, place it in a clean, dry metal or glass 
container, which must be filled with the sample, closéd with a 
tight cover, sealed, marked, and sent to the laboratory for test 
with the inspector’s report on caking in container. 


Specification jor Titanium Pigment 3 


When requested, a duplicate sample may be taken from the 
same package and delivered to the seller, and the inspector may - 
take a third sample to hold for test in case of dispute. 


3. LABORATORY EXAMINATION, DRY PIGMENT. 


(a) Coror.—Take 5 g of the sample, add 1.5 cc of linseed oil, 
rub up on a stone slab or glass plate with a flat-bottomed glass or 
stone pestle or muller to a uniform smooth paste. Treat in a simi- 
lar manner 5 g of the standard titanium pigment. Spread the 
two pastes side by side on a clear, colorless glass plate and compare 
the colors. If the sample is as white as or whiter than the “ stand- 
ard,”’ it passes this test. If the ‘‘standard” is whiter than the 
sample, the material does not meet the specification. 

(6) Color StTRENGTH.—Weigh accurately 0.01 g of lamp- 
black, place on a large glass plate or stone slab, add o.2 cc of lin- 
seed oil and rub up with a flat-bottomed glass pestle or muller, 
then add exactly 10 g of the sample and 2.5 cc of linseed oil, and 
grind with a circular motion of the muller 50 times; gather up 
with a sharp-edged spatula and grind out twice more in a like 
manner, giving the pestle a uniform pressure. ‘Treat another 
0.o1 g of lampblack in the same manner, except that 10 g of stand- 
ard titanium pigment is used instead of 10g of the sample. Spread 
the two pastes side by side on a glass microscope slide and com- 
pare the colors. If the sample is as light as or lighter in color 
than the “standard,” it passes this test. If the ‘‘standard”’ is 
lighter in color than the sample, the material does not meet the 
specification. 

(c) COARSE PARTICLES.'—Dry in an oven at 105 to 110° C. a 
No. 325 sieve, cool, and weigh accurately. Weigh 10 g of the 
sample, wash with water through the sieve, breaking up all lumps 

either by gentle pressure with a pestle in a mortar, but not grind- 
| ing, or with a brush on the sieve. After washing with water until 
all but the particles too coarse to pass the sieve have been washed 
through, dry the sieve for one hour at 105 to 110° C., cool, and 
weigh. 

(d) QUALITATIVE ANALYSIS.—Place a small amount (about one- 
half gram) of the sample in a 250 cc Pyrex glass beaker; add 20 
ce of concentrated sulphuric acid and 7 to 8 g of ammonium sul- 
phate. Mix well, and boil for a few minutes. The sample should 

1 For a general discussion of sieve tests of pigments and data regarding many pigments on the market seed 


Circular No. 148 of the Educational Bureau, scientific section, Paint Manufacturers’ Association of the 
United States. 


4 Circular of the Bureau of Standards. 


go completely into solution; a residue denotes the presence of 
silica or siliceous matter. Cool the solution, dilute with 100 cc 
of water, heat to boiling, settle, filter, wash with hot 5 per cent 
sulphuric acid until free from titanium, and test the residue for 
lead, etc. ‘Test the filtrate for calcium, zinc, iron, chromium, etc., 
by regular methods of qualitative analysis. For the iron deter- 
mination take a portion of the filtrate, add 5 g of tartaric acid, 
make slightly ammoniacal, pass in hydrogen sulphide in excess, 
and digest at the side of a steam bath for a while. No precipitate 
denotes absence of iron, nickel, cobalt, lead, copper, ete. A 
black precipitate easily soluble in dilute hydrochloric acid denotes 
iron. For titanium test a small portion of the original filtrate 
with hydrogen peroxide (a clear yellow-orange color should result) 
and another portion with metallic tin or zine (a vee blue to violet 
coloration should result). 

The pigment should show negative tests for sulphide sulphur, 
carbonates, and appreciable water-soluble matter. 

(ec) MoisturE.—Place 1 g of the sample in a wide-mouth, short 
weighing tube provided with a glass stopper. Heat with the stop- 
per removed for two hours at a temperature between 105 and 110° 
C. Insert the stopper, cool, and weigh. Calculate the loss in 
weight as moisture. 

(f) MATTER SOLUBLE IN WATER.—Transfer 2.5 g of the pigment 
to a graduated 250 cc flask, add 100 cc of water, boil for five 
minutes, cool, fill to the mark with water, mix, and allow to 
settle. Pour the supernatant liquid through a dry filter paper 
and discard the first 20 cc. ‘Then evaporate roo cc of the clear 
filtrate to dryness in a weighed dish, heat for one hour at 105 to 110° 
C., cool, and weigh. 

(g) Tyrantum Oxipk.—Transfer 0.5 g of the dried sample to a 
250 cc Pyrex beaker, add 20 cc of concentrated sulphuric acid 
and 7 to 8 g of ammonium sulphate. Mix well and heat on a hot 
plate until fumes of siiphuric acid are evolved, and then con- 
tinue the heating over a strong flame until solution is complete 
(usually not over five minutes of boiling) or it is apparent that the 
residue is composed of silica or siliceous matter. Caution should 
be observed in visually examining this hot solution. Cool the 
solution, dilute with 100 ce of water, stir, heat carefully to boiling 
while stirring, settle, filter through paper and transfer the precipi- 
tate completely to the paper. Wash the insoluble residue with 
cold 5 per cent (by volume) sulphuric acid until titanium is 
removed. 


Specification for Titanium Pigment. 5 


Dilute the filtrate to 200 cc and add about 10 ce of ammonia, 
specific gravity 0.90, to lower the acidity to approximately 5 
per cent sulphuric acid (by volume). 

Wash out a Jones reductor ? with dilute 5 per cent (by volume) 
sulphuric acid and water, leaving sufficient water in the reductor 
to fill to the upper level of the zinc. (These washings should 
require not more than one or two drops of o.1 N potassium per- 
manganate solution to obtain the pink color.) Empty the 
receiver, and put in it 25 cc (measured in a graduate) of ferric 
sulphate solution. (See Reagents.) Reduce the prepared tita- 
nium solution as follows: (1) Run 50 cc of the 5 per cent sulphuric 
acid solution through the reductor at a speed of about 100 cc 
per minute; (2) follow this with the titanium solution; (3) wash 
out with 100 cc of 5 per cent sulphuric acid; (4) finally run through 
about 100 cc of water. 

Care should be observed that the reductor is always filled with 
solution or water to the upper level of the zinc, 

Gradually release the suction, wash thoroughly the glass tube 
that was immersed in the ferric sulphate solution, remove the 
receiver, and titrate immediately with 0.1 N potassium perman- 
ganate solution. (See Reagents.) 

1 cc o.1 N KMnO,=0.00481 g Ti 
=0.00801 g TiO, 

Run a blank determination, using the same reagents, washing 
the reductor as in the above determination. Subtract this per- 
manganate reading from the original reading and calculate the 
final reading to titanium dioxide (TiO,) (which will include iron, 
chromium, arsenic, and any other substance which is reduced by 
zinc and acid). (See 3 (2) for reporting TiO,,.) 3 

(h) DETERMINATION OF BARIUM SULPHATE.—Ignite and weigh 
the precipitate of BaSO, obtained in separating the titanium.‘ 
(See 3 ().) | 

(1) IRON OxipE.—Prepare a standard ferric solution contain- 
ing 0.00001 g Fe per cc. (See Reagents.) Weigh ar g portion 
of the sample and treat as in 3 (g), transfer without filtering to a 
200 ce flask, cool, fill to the mark, and determine iron colorimetri- 
cally in 50 cc aliquots in the following manner. Filter through a 


2 Directions for preparing a Jones reductor may be found in Blair, ‘‘ The Chemical Analysis of Iron,” 
&th ed. Lippincott & Co., or Treadwell-Hall, ‘‘ Analytical Chemistry,” sth ed. J. Wiley & Sons, p. 638 
8 Any other accurate method of determining titanium oxide may be used. For a discussion of various 
methods see ‘‘The Analysis of Silicate and Carbonate Rocks,” by W. F. Hillebrand, U. S. Geological 
Survey Bulletin 700. ; 
‘If the sample is impure it may be necessary to purify this precipitate, using appropriate methods. 
84628°—24 2 


6 Circular of the Bureau of Standards 


dry filter paper (discarding the first 20 cc), and transfer 50 cc 
of the filtrate to a clean roo ce Nessler tube or other color com-’ 
parator. Add a drop or two of 0.1 N KMnO, solution, to oxidize 
any ferrous iron until a faint pink color is obtained. Add 10 cc 
of ammonium or potassium thiocyanate solution (see Reagents), 
dilute to 100 cc, and mix thoroughly. Compare the color imme- 
diately with a series of standards, prepared side by side with the 
sample in similar tubes. 

Prepare the standards from the standard ferric solution so as 
to have a range of from 0.000005 g Fe to 0.00004 g (0.5 to 4.0 cc). 
Dilute these amounts with distilled water to about 50 cc. Add 
just enough o.1 N KMn0O, to produce a faint pink and then 10 ec 
of the thiocyanate solution. Finally dilute all standards to 100 cc. 

For a single sample it is more convenient to run the standard Fe solution from a 
burette into a Nessler tube containing the acid, 10 cc of the thiocyanate solution, and 
60 to 70 cc of distilled water until the depth of the color thus produced on dilution 
to 100 cc and mixed exactly matches the sample. From the burette reading calculate 
the amount of Fe. The color comparisons must be made immediately after the stand- 
ards are prepared. 

Calculate the total iron found to Fe,O, and report as such. 
Calculate the TiO, equivalent by multiplying by the factor 1.003 
and subtract this figure from the total titanium oxide as deter- 
mined in 3 (g) and report the remainder as TiO,. 


4. LABORATORY EXAMINATION, PASTE. 


(a) CAKING IN CONTAINER.—When an original package is re- 
ceived in the laboratory it shall be weighed, opened, and stirred 
with a stiff spatula or paddle. The paste must be no more diffi- 
cult to break up and show no more caking than a normal good 
grade of titanium pigment paste. The paste shall finally be 
thoroughly mixed, removed from the container, the container 
wiped clean, and weighed. This weight subtracted from the 
weight of the original package gives the net weight of the con- 
tents. A portion of the thoroughly mixed paste shall be placed 
in a clean container, and the portions for the remaining tests 
promptly weighed out. 

(6) MIxING witH LINSEED O1L.—One hundred grams of the paste 
shall be placed in a cup, 40 cc of linseed oil added slowly with 
careful stirring and mixing with a spatula or paddle. The re- 
sulting mixture must be smooth and of good brushing consistency. 
Flow a portion of this paint on a clean glass plate. Let standina 
nearly vertical position at room temperature (65 to 100° F.). 


Specification for Titanium Pigment. ‘i 


The film after four hours shall show no streaking or separation: 
within a distance of 4 inches from the top. 

(c) MoIstuRE AND OTHER VOLATILE MATTER.—Weigh ac- 
curately from 3 to 5 g of the paste into a tared flat-bottomed 
dish, about 5 cm in diameter, spreading the paste over the bottom. 
Heat at 105 to 110° C. for one hour, cool, and weigh. Calculate 
the loss in weight as the percentage of moisture and other volatile 
matter. 

(d) PERCENTAGE OF PIGMENT.—Weigh accurately about 15 g 
of the paste into a weighed centrifuge tube. Add 20 to 30 ce 
of “extraction mixture’ (see Reagents), mix thoroughly with a 
glass rod, wash the rod with more of the extraction mixture, and 
add sufficient of the reagent to make a total of 60 cc in the tube. 
Place the tube in the container of a centrifuge, surround with: 
water, and counterbalance the container of the opposite arm with 
a similar tube or a tube with water. Whirl at a moderate speed 
until clear. Decant the clear supernatant liquid. Repeat the 
extraction twice with 40 cc portions of extraction mixture, and once 
with 40 cc of ether. After drawing off the ether, set the tube in a 
beaker of water at about 80° C. or on top of a warm oven for 10 
minutes, then in an oven at 110 to 115° C. for two hours. Cool, 
weigh, and calculate the percentage of pigment. 

(e) EXAMINATION OF PiGMENT.—Grind the pigment from (d) 
to a fine powder, pass through a No. 80 sieve to remove any 
“skins,” and preserve in a stoppered tube and apply tests 3 (d), 
(7), (9), (2), and (7). If required, apply tests 3 (a) and (b) in 
comparison with a portion of pigment extracted from the standard 
paste in exactly the same manner as in extracting the sample. 

(7) PREPARATION oF Farry Actps.—To about 25 g of the paste 
in a porcelain casserole add 15 cc of aqueous sodium hydroxide 
(see Reagents), and 75 cc of ethyl alcohol, mix and heat uncovered 
on a steam bath until saponification is complete (about one hour). 
Add too cc of water, boil, add sulphuric acid of specific gravity 
1.2 (8 to 10 cc in excess), boil, stir, and transfer to a separatory 
funnel to which some water has been previously added. Draw 
off as much as possible of the acid aqueous layer, wash once with 
water; then add 50 cc of water and 50 cc of ether. Shake very 
gently with a whirling motion to dissolve the fatty acids in the 
ether, but not violently, so as to avoid forming an emulsion. 
Draw off the aqueous layer and wash the ether layer with one 15 
cc portion of water and then with 5 cc portions of water until free 
from sulphuric acid. Then draw off completely the water layer. 


8 Circular of the Bureau of Standards. 


Transfer the ether solution to a dry flask, and add 25 to 50 g of 
anhydrous sodium sulphate. Stopper the flask and let stand with 
occasional skaking at a temperature below 25° C. until the water 
is completely removed from the ether solution, which will be 
shown by the solution becoming perfectly clear above the solid 
sodium sulphate. Decant this clear solution (if necessary through 
a dry filter paper) into a dry roo cc Erlenmeyer flask. Pass a 
rapid current of dry air (pass through a CaCl, tower) into the 
mouth of the Erlenmeyer flask and heat to a temperature below 
75°C. on a dry hot plate until the ether is entirely driven off. 

It is important to follow all of the details, since ether generally 
contains alcohol, and afler washing with water always contams 
water. It is very difficult to remove water and alcohol from fatty 
acids by evaporation, but the washing of the ether solution and sub- 
sequent drying with anhydrous sodium sulphate removes both water 
and alcohol. Ether, in the absence of water and alcohol, 1s easily 
removed from faity acids by gentle heat. 

The fatty acids prepared as above should be kept in a stoppered 
flask and examined at once. 

(g) TEST FOR MINERAL OIL AND OTHER UNSAPONIFIABLE MAT- 
TER.—Place 10 drops of the fatty acid (f) ina 50 cc test tube, add 
5 cc Of alcoholic soda (see Reagents), boil vigorously for five min- 
utes, add 4o ce of water, and mix; a clear solution indicates that 
not more than traces of unsaponifiable matter are present. If 
the solution is not clear, the oil is not pure linseed oil. 

(h) IODINE — oF Farry Acips.—Place a small quantity 
of the fatty acids! (f) in a small weighing burette or beaker. 
Weigh accurately. | Transfer (by dropping) about 0.15 g (0.10 to 
0.20 g) to a 500 cc} bottle having a well-ground glass stopper, or 
an Erlenmeyer flask having a specially flanged neck for the iodine 
test. Reweigh the) burette or beaker and determine the amount 
of sample used. Add ro cc of chloroform. Whirl the bottle to 
dissolve the sample. Add 1o ce of chloroform to two empty 
bottles like that used for the sample. Add toeach bottle 25 cc of 
the Hanus solution (see Reagents) and let stand, with occasional 
shaking, for one-half hour. Add ro cc of the 15 per cent potas- 
sium-iodide solution and 100 cc of water, and titrate with standard 
sodium thiosulphate, using starch as indicator. ‘The titrations on 
the two blank tests should agree within 0.1 cc. From the iodine 
value of the thiosulphate solution and the difference between the 
average of the blank titrations and the titration on the sample, 
calculate the iodine number of the sample tested. (lodine number 


Specification for Titanium Pigment. 9 


is centigrams of iodine to 1 g of sample.) If the iodine number is 
less than 170, the oil does not meet the specification. 

(2) COARSE PARTICLES AND SKINS.—Dry in an oven at 105 to 
110° C. a No. 325 sieve. Weigh an amount of paste containing 
10 g of pigment (see 4 (d)), add 100 cc of kerosene, mix thoroughly, 
and wash with kerosene, through the sieve, breaking up all lumps but 
not grinding. After washing with kerosene until all but particles 
too coarse to pass the sieve have been washed through, wash all 
kerosene from the sieve with ether or petroleum ether, heat the 
sieve for one hour at.105 to 110° C., cool, and weigh. 


5. REAGENTS. 


(a) EXTRACTION MIxTURE.— 

10 volumes ether (ethyl ether). 
6 volumes benzol. 
4 volumes methyl alcohol. 
I volume acetone. 

(b) AguEous Soprum HyproxipEe.—Dissolve 100 g sodium 
hydroxide in distilled water and dilute to 300 ce. 

(c) STANDARD SopiuM THIOSULPHATE SOLUTION.— Dissolve pure 
sodium thiosulphate in distilled water that has been well boiled to 
free it from carbon dioxide, in the proportion of 24.83 g of crys- 
tallized sodium thiosulphate to 1,000 cc of the solution. It is 
best to let this solution stand for about two weeks before standard- 
izing. Standardize with pure resublimed iodine.’ ‘This solution 
will be approximately decinormal, and it is best to leave it as it is 
after determining its exact iodine value rather than to attempt to 
adjust it to exactly decinormal. Preserve in a stock bottle pro- 
vided with a guard tube filled with soda lime. 

(d) STARCH SOLUTION.—Stir up 2 to 3 g of potato starch or 5 
g of soluble starch with 100 cc of 1 per cent salicylic acid solution, 
add 300 to 400 cc of boiling water, and boil the mixture until the 
starch is practically dissolved, then dilute to 1 liter. 

(e) Potasstum IopipE SoLuTIon.—Dissolve 150 g of potassium 
iodide free from iodate in distilled water, and dilute to 1,000 cc. 

(f) HANUS SOLUTION.—Dissolve 13.2 g of iodine im 1,000 cc 
of 99.5 per cent glacial acetic acid which will not reduce chromic 
acid. Add enough bromine to double the halogen content, 
determined by titration (3 cc of bromine is about the proper 


’ Tread well-Hall, Analytical Chemistry, 2, sth ed., p. 645. 


IO Circular of the Bureau of Standards. 


amount). The iodine may be dissolved by the aid of heat, but 
the solution should be cold when the bromine is added. 

(g) ALconotic Sopium HyproxinE SoLuTIoN.—Dissolve pure 
sodium hydroxide in 95 per cent ethyl alcohol in the proportion of 
about 22 g per 1,000 cc. Let stand in a stoppered bottle. De- 
cant the clear liquid into another bottle and keep well stoppered. 
This solution should be colorless or only slightly yellow when 
used, and it will keep colorless longer if the alcohol is previously 
treated with sodium hydroxide (about 80 g to 1,000 cc), kept at 
about 50° C. for 15 days and then distilled. 

(hk) 0.1 N Porasstum PERMANGANATE SOLUTION.—Dissolve 
3.161 g of pure potassium permanganate in a liter of distilled 
water, let stand 8 to 14 days, siphon off the clear solution (or 
filter through an asbestos filter), and standardize as follows: In 
a 400 cc beaker dissolve 0.25 to 0.30 g of Bureau of Standards’ 
sodium oxalate in 250 cc of hot water (80 to 90° C.) and add 15 
cc of dilute sulphuric acid (1:1). Titrate at once with the potas- 
sium permanganate solution, stirring the lquid vigorously and 
continuously. The permanganate must not be added more 
rapidly than 10 to 15 ce per minute, and the last 0.5 to r cc must 
be added dropwise with particular care to allow each drop to be 
fully decolorized before the next is introduced. The solution 
should not be below 60° C. by the time the end point is reached. 
(More rapid cooling may be prevented by allowing the beaker to 
stand on a small asbestos-covered hot plate during the titration. 
The use of a small thermometer as a stirring rod is most convenient.) 
The weight of sodium oxalate used multiplied by 0.8334 gives its 
iron equivalent, or multiplied by 1.1954 gives its titanium dioxide 
(TiO,) equivalent*. The permanganate solution should be kept 
in a glass-stoppered bottle painted black to keep out light. 

(i) FERRIC SULPHATE SOLUTION For TrTanrumM.—A solution 
containing 2 per cent of iron as ferric sulphate is desired and may 
be prepared as follows: Dissolve 20 g of pure iron or plain carbon 
steel in a slight excess of hydrochloric acid, oxidize with nitric 
acid, heat with about 80 cc of sulphuric acid until fumes are 
evolved, finally cool, and dilute to 1,000 cc, set on steam bath, 
until dissolved, and filter if necessary. Add o.1 N permanga- 
nate solution until a faint pink color shows that any ferrous iron 
has been oxidized. Ferric ammonium sulphate may also be used’. 


6 International Atomic Weights, 1921-22. 
7 Gooch, Methods in Chemical Analysis, 1st ed., p. 426. 


Specification for Titanium Pigment. II 


(7) STANDARD FERRIC SULPHATE SOLUTION FOR COLORIMET- 
RIC DETERMINATION OF IRON.—Determine the strength of the 
ferric solution reagent used in 5 (i) in terms of iron and dilute 
this solution until one is obtained of the strength 1 cc =0.00001 
g Fe. 

(k) Potasstum TurocyaNaTe INDICATOR.—Prepare a 2 per 
cent solution of the pure salt in distilled water. 


ADDITIONAL COPIES 
OF THIS PUBLICATION MAY BE PROCURED FROM 
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U. S. Gov’t 
Master 
Specification, 


No. 137 
DEPARTMENT OF COMMERCE 


BUREAU OF STANDARDS 


George K. Burgess, Director 


CIRCULAR OF THE BUREAU OF STANDARDS, No. 165 


[Issued June 21, 1924] 


UNITED STATES GOVERNMENT MASTER SPECIFICATION FOR 
OLIVE DRAB PAINT (SEMIPASTE AND READY-MIXED) 


FEDERAL SPECIFICATIONS BOARD SPECIFICATION No. 137 


This specification was officially adopted by the Federal Specifications Board 
on May 1, 1924, for the use of the Departments and Independent Establishments 
of the Government in the purchase of olive drab paint (semipaste and ready- 
mixed) 


CONTENTS 


4. Laboratory examination, ready-mixed PaintLe se et Fee 

ETN TOs ge ARCS oe ek” < eae alga aE PERE SC aaan aaC LS 
remeruerrere HEC WAPI 0S NN ee 11 
Perro moore IB tOrmatlon 7 eS e N De As Serme eee eee nd 
Poa eer epeciiicatiting. cu) ole kc er eee 11 


I. CLASSES 
Olive drab paint shall be of the following classes: Semipaste in 


lineseed oil and ready mixed. 
102446°—24 


yt CIRCULAR OF THE BUREAU OF STANDARDS 


II. MATERIAL 
No details. 
III. GENERAL REQUIREMENTS 
No details. 
IV. DETAIL REQUIREMENTS 


1. PIGMENT 


The pigment shall be composed of: 


Ingredients % Maximum | Minimum 


Per cent Per cent 
White lead (basic carbonate, basic sulphate, or a mixture thereof) --.....---.----|-------.---- 35 


PAU OXUAS CLO) hss Re i a ie oka Ped pts Meets! S 30 
White mineral pigments (containing no lead or zinc compounds), pure tinting 

colors, or. any mixture thereof. . 225.225 2226.55 nen soos sean e ee BO. Peas ae 
PirearG GOlOTS oS ee ecu pa acw een Laveen mecha eee geet Noten (Sec. ee 
al lOnIGe SUL DAU oo 8 oo ee er 2 oo a a ai eee ee IN On@s; Ae so osee 


In no case shall the sum of the basic lead carbonate, basic lead 
sulphate, and zinc oxide be less than 70 per cent. The lead and 
zinc pigments may be introduced in the form of any mixture pre- 
ferred of basic carbonate white lead, basic sulphate white lead, zinc 
oxide, or leaded zinc, provided the above requirements as to compo- 
sition are met. 

The difference between the total lead weighed as lead sulphate 
and the lead sulphate equivalent to the chromium found, multiplied 
by the factor 0.883 shall be considered white lead. It is not possible 
to determine the amount of lead carbonate and lead sulphate when 
carbonates or sulphates of other metals, such as calcium, are present. 
Also neither basic lead carbonate nor basic lead sulphate is a definite 
compound. The factor to convert PbSO, to (PbCO,), Pb(OH), is 
0.854, to convert PbSO, to PbSO,PbO is 0.868, and to convert PbSO, 
to (PbSO,), PbO is 0.913. The arbitrary factor used under this 
specification is the mean of the largest and smallest of these three 
factors. | 

2. LIQUID 


The liquid in semipaste paint shall be entirely pure raw or refined 
linseed oil; in ready-mixed paint it shall contain not less than 85 
per cent pure raw linseed oil, the remainder to be combined drier 
and thinner. The thinner shall be turpentine, volatile mineral 
spirits, or a mixture thereof. 


3. SEMIPASTE 


Semipaste shall be made by thoroughly grinding the pigment 
with pure raw or refined linseed oil. 

The semipaste as received, and three months thereafter, shall be 
not caked in the container and shall break up readily in linseed oil to 


SPECIFICATION FOR OLIVE DRAB PAINT 3 


form a smooth paint of brushing consistency. It shall mix readily 
with linseed oil, turpentine, or volatile mineral spirits, or any com- 
bination of these substances, in all proportions without curdling. 
The color and hiding power when specified shall be equal to those of 
a sample mutually agreed upon by buyer and seller. The weight 
per gallon shall be not less than 18 pounds. The paste shall con- 
sist of: 


Ingredients Maximum | Minimum 


Per cent Per cent 
77 


ga REE a a ed eee ae A ee oe 73 
NR ee ca wk ip sn amore mene ek 27; 23 
Moisture and ofher volatile matter... | _.0.....-..20.---- 2 n 0.7 |azoues ee 
Coarse particles and ‘‘skins’’ (total residue retained on No. 325 sieve based on 

OE BE eh) es SS ae oe ey > ee MMe tine Oe) Wee ge ee 2H0ne Soe ees ae 


4. READY-MIXED PAINT 


Ready-mixed paints shall be well ground, shall not settle badly or 
cake in the container, shall be readily broken up with a paddle to a 
smooth uniform paint of good brushing consistency, and shall dry 
within 18 hours to a full oil gloss without streaking, running, or 
sagging. The color and hiding power when specified shall be equal 
to those of a sample mutually agreed upon by buyer and seller. The 
weight per gallor shall be not less than 15 pounds. The paint shall 
consist of: 


Ingredients Maximum | Minimum 
Per cent Per cent 
Seen ie mee ce ate ee ee ee ee ceth 66 62 
Liquid (containing at least 85 per cent linseed oil) ______________________________- 38 34 
ee SPLEEN SO 6 Car eR A Eh ee. OI BS, NR in dN 0: 6 lege cnees ee 
Coarse particles and ‘‘skins’’ (total residue retained on No. 325 sieve based on 


eS Breer Ps a ed fs ee Sa ee 2:0: 225. eee 


V. METHODS FOR SAMPLING AND TESTING 


Delweries will, in general, be sampled and tested by the following 
methods, but the purchaser reserves the right to use any additional 
avatlable information to ascertain whether the material meets the 
specification. 

1. SAMPLING 


Tt is mutually agreed by buyer and seller that a single package out 
of each lot of not more than 1,000 packages shall be taken as repre- 
sentative of the whole. Whenever possible an original unopened 
container shall be sent to the laboratory, and when this is for any 
reason not done, the inspector shall determine by thorough testing 
with a paddle or spatula whether the material meets the requirement 
regarding caking in the container. He shall then thoroughly mix 


4 CIRCULAR OF THE BUREAU OF STANDARDS 


the contents of the container and draw a sample of not less than 5 
pounds of the thoroughly mixed paint, place it in a clean, dry metal 
or glass container, which must be filled with the sample, closed with 
a tight cover, sealed, marked, and sent to the laboratory for test with 
the inspector’s report on caking in container. 

When requested, a duplicate sample may be taken from the same 
package and delivered to the seller, and the inspector may take a 
third sample to hold for test in case of dispute. 


2. LABORATORY EXAMINATION, SEMIPASTE 


(a) Canine 1In Contarner.—When an original package is received 
in the laboratory it shall be weighed, opened, and stirred with a stiff 
spatula or paddle. The paste must be no more difficult to break up 
than a normal good grade of semipaste paint. The semipaste shall 
finally be thoroughly mixed, removed from the container, and the 
container wiped clean and weighed. This weight subtracted from 
the weight of the original package gives the net weight of the con- 
tents. A portion of thoroughly mixed semipaste shall be placed in 
a clean container and the portions for the Lae tests promptly 
weighed out. 

(6) WereutT per Gatton.—From the weight of a known volume 
of the paste calculate the specific gravity, which multiplied by 8.33 
gives the weight in pounds per gallon. Any suitable container of 
known volume may be used for the purpose, but. a short cylinder of 
heavy glass with rounded bottom about 75 mm high and having 
a capacity of from 125 to 175 ce (a glass cap to keep dust from re- 
agent bottle stopper) is a convenient. vessel, for the purpose. The 
capacity of this vessel is determined to within 1 cc. The paste is 
packed into it until completely full, the top leveled off smooth with a 
spatula, and weighed_to plus or minus 0.5 g. Subtract the weight of 
the empty container and divide the remainder by the number of 
cubic centimeters representing the capacity of the container. The 
quotient is the specific gravity, which can be thus determined within 
plus or minus 2 in the second decimal place. 

(c) Mrxine wirn Linszep Orn.—One hundred grams of the paste 
shall be placed in a cup, 18 ec of linseed oil added slowly with care- 
ful stirring and mixing with a spatula or paddle. The resulting 
mixture must be smooth and of good brushing consistency. 

(qd) Cotor—To the mixture made, in (¢), add 3 ce of drier 
(F. S. B. No. 20) and mix thoroughly. Prepare a mixture of the 
standard paste with 18 cc of linseed oil and 3 ce of drier, using 
the same linseed oil and drier for both lots of paint. Apply both 
paints on clean metal or glass so that the edges touch one another. 
Let dry and compare the colors. 


eee a 
2S 


SPECIFICATION FOR OLIVE DRAB PAINT 5 


(¢) Moisrure anp Oruzr Voiatite Marrer.—Weigh accurately 
from 3 to 5 g of the paste in a tared flat-bottomed dish about 5 
cm in diameter, spreading the paste over the bottom. Heat at 105 
to 110° C. for one hour, cool, and weigh. Calculate the loss in 
weight as the percentage of moisture and volatile matter. 

(7) Prrcenrace or Picmenr.—Weigh accurately about 15 g of 
the paste in a weighed centrifuge tube. Add 20 to 30 ce of “ex- 
traction mixture” (see Reagents), mix thoroughly with a glass rod, 
wash the rod with more of the extraction mixture, and add enough 
of the reagent to make a total of 60 cc in the tube. Place the tube 
in the container of a centrifuge, surround with water, and counter- 
balance the container of the opposite arm with a similar tube or 
a tube with water. Whirl at a moderate speed until well settled. 
Decant the clear supernatant liquid, repeat the extraction twice with 
40 ce of extraction mixture and once with 40 cc of ether. After 
drawing off the ether, set the tube in a beaker of water at about 
80° C. or on top of a warm oven for 10 minutes, then in an oven 
at 110 to 115° C. for two hours. Cool, weigh, and calculate the 
percentage of pigment. Grind the pigment to a fine powder, pass 
through a No. 80 sieve to remove any skins, and preserve in a 
stoppered bottle. 

(g) Preparation or Farry Aciwws.—To about 25 g of the paste in 
a porcelain casserole, add 15 cc of aqueous sodium hydroxide (see 
Reagents) and 75 cc of ethyl alcohol, mix and heat uncovered on a 
steam bath until saponification is complete (about one hour). Add 
100 ce of water, boil, add sulphuric acid of specific gravity 1.2 (8 to 
10 ce in excess), boil, stir, and transfer to a separatory funnel to 
which some water has been previously added. Draw off as much as 
possible of the acid aqueous layer and lead sulphate precipitate, wash 
once with water, then add 50 cc of water and 50 cc of ether. 
Shake very gently with a whirling action to dissolve the fatty 
acids in the ether, but not so violently as to form an emulsion. Draw 
off the aqueous layer and wash the ether layer with one 15 ce por- 
tion of water and then with 5 cc portions of water until free from 
sulphuric acid. Then draw off the water layer completely. Transfer 
the ether solution to a dry flask and add 25 to 50 g of anhydrous 
sodium sulphate. Stopper the flask and let stand with occasional 
shaking at a temperature below 25° C. until the water is completely 
removed from the ether solution, which will be shown by the solu- 
tion becoming perfectly clear above the solid sodium sulphate. De- 
cant this clear solution, if necessary, through, a dry filter paper into 
a dry 100 cc Erlenmeyer flask. Pass a rapid current of dry air 
(pass through a CaCl, tower) into the mouth of the Erlenmeyer 
flask and heat to a temperature below 75° C. on a dry, hot plate 
until the ether is entirely driven off. 


6 CIRCULAR OF THE BUREAU OF STANDARDS 


It is important to follow all of the details, since ether generally 
contains alcohol, and after washing with water always contains 
water. It is very difficult to remove water and alcohol by evapora- 
tion from fatty acids, but the washing of the ether solution and 
subsequent drying with anhydrous sodium sulphate removes both 
water and alcohol. Ether, in the absence of water and alcohol, is 
easily removed from fatty acids by gentle heat. 

The fatty acids prepared as above should be kept in a stoppered 
flask and examined at once. 

(2) Txsr ror Minera Orn anp OrHer UNSAPONIFIABLE Marrer.— 
Place 10 drops of the fatty acid, (7), in a 50 ce test. tube, add 5 ce 
of alcoholic soda (see Reagents), boil vigorously for five minutes, add 
40 cc of water, and mix; a clear solution indicates that not more 
than traces of unsaponifiable matter are present. If the solution is 
not clear, the oil is not pure linseed oil. 

(2) Ioptns Numper or Farry Acips.—Place a anit quantity of 
the fatty acids, (7), in a small weighing burette or beaker. Weigh 
accurately. ‘Transfer by dropping about 0.15 g (0.10 to 0.20 g) 
into a 500 cc bottle having a well-ground glass stopper, or an Erlen- 
meyer flask having a specially flanged neck for the iodine test. Re- 
weigh the burette or beaker and determine the amount of sample 
used. Add 10 cc of chloroform. Whirl the bottle to dissolve the 
sample. Add 10 cc of chloroform to two empty bottles like that 
used for the sample. Add to each bottle 25 cc of the Hanus solu- 
tion (see Reagents) and let stand with occasional shaking for one- 
half hour. Add 10 cc of the 15 per cent potassium iodide solution 
and 100 ce of water, and titrate with standard sodium thiosulphate, 
using starch as indicator. The titrations on the two blank tests 
should agree within 0.1 cc. From the difference between the aver- 
age of the blank titrations and the titration on the sample and the 
iodine value of the thiosulphate solution, calculate the iodine number 
of the sample tested. (Iodine number is centigrams of iodine to 1 
g of sample.) If the iodine number is less than 170, the oil does 
not meet the specification. 


(7) Coarse Parrictes anp Sxins.—Dry in an oven at 105 to , 


110° C. a No. 325 sieve, cool, and weigh accurately. Weigh an amount 
of semipaste containing 10 g of pigment (see V 2 (7)), add 100 ce 
of kerosene, mix thoroustily, and wash with kerosene through the 
sieve, breaking up all lumps, but not grinding. After washing with 
kerosene until all but the particles too coarse to pass the sieve have 
been washed through, wash all kerosene from the sieve with ether 
or petroleum ether, heat the sieve and contents for one hour at 
105 to 110° C., cool and weigh. 


a 


SPECIFICATION FOR OLIVE DRAB PAINT 7 
3. ANALYSIS OF PIGMENT 


(a) Quarrrarive Anatysis.—A complete qualitative analysis, fol- 
lowing the well-established methods, is always advisable. Test a 
portion of the pigment with hydrochloric acid (1: 1). No odor of 
hydrogen sulphide should develop. Boil, dilute, filter, and test 
the filtrate for metals other than lead and zinc (especially calcium 
and barium). The absence of calcium in this filtrate indicates that 
the extending pigments contain no calcium carbonate or calcium sul- 
phate; the absence of barium indicates that the extending pigments 
contain no barium carbonate. To test for chromate, boil another 
small portion of the pigment. with dilute nitric acid, filter, cool, and 
add to the filtrate a few cubic centimeters of ether and a few drops of 
hydrogen peroxide; stir, let stand until the ether layer separates. If 
this layer is deep blue, chromium is indicated. Test for Prussian blue 
(which is rarely present) by boiling a portion of the pigment with 
sodium hydroxide solution. A yellow or yellow-brown precipitate 
_ with a yellow liquid above it should result. Filter, add to the 
filtrate a mixture of ferric and ferrous salts, and render acid with 
dilute hydrochloric acid. A blue color indicates the presence of 
Prussian blue in the sample. 

(6) Wuire Leap—Weigh accurately about 1 ¢ of the pigment, 
transfer to a 250 cc beaker, moisten with a few drops of alcohol, add 
slowly 25 cc of concentrated hydrochloric acid, cover, and boil for 
5 to 10 minutes. Dilute to about 150 cc with hot water and boil 
for 5 to 10 minutes. Filter on paper or on a Gooch crucible, and 
wash the insoluble residue thoroughly with hot water. Discard the 
residue for quantitative purposes. Nearly neutralize with ammonia 
the filtrate from the insoluble matter, dilute to about 300 ce and pass 
into the clear solution a rapid current of hydrogen sulphide to com- 
plete precipitation, let the sulphide of lead settle, filter on paper, 
wash with water containing some hydrogen sulphide, dissolve the 
sulphide in hot nitric acid (1:3), add 10 cc of sulphuric acid (1:1), 
evaporate until copious fumes of sulphuric anhydride are evolved; 
cool, add about 75 ce of water, and then about 75 cc of 95 per cent 
ethyl alcohol. Stir, let settle, filter on a Gooch crucible, wash with 
dilute alcohol, dry, ignite, and weigh as PbSO,: Subtract the lead 
sulphate equivalent of the total cromium as found below, (c), multiply 
the remaining PbSO, by the factor 0.883 and report as white lead. 

(c) Toran Curomrum.—Heat the filtrate from the lead sulphide 
to expel hydrogen sulphide. Cool, add sodium peroxide, keeping the 
beaker covered, in sufficient amount to render the solution alkaline 
and to oxidize the chromium to chromate. Boil until all the hydro- 
gen peroxide is driven off, cool, acidify with sulphuric acid (1:4), 
add a measured excess of a freshly prepared solution of ferrous sul- 


8 CIRCULAR OF THE BUREAU OF STANDARDS 


phate, and titrate the excess of ferrous iron with standard potassium 
dichromate, using potassium ferricyanide solution as outside indica- 
tor. Titrate a blank of an equal volume of the ferrous sulphate solu- 
tion with the standard potassium dichromate. From the difference 
between the titration on the blank and on the sample, calculate the 
chromium in the sample to PbCrO,. From the PbCrO, found, cal- 
culate the equivalent of PbSO, by multiplying by the factor 0.938. 

(d) Zinc Oxwwn.—Weigh accurately about 1 g of the pigment, 
transfer to a 250 cc beaker, moisten with alcohol, add 30 ec of 
hydrochloric acid (1:2), boil for two or three minutes, add about 
100 cc of water, let settle, and filter on paper; to the filtrate add 
about 2 g of ammonium chloride and strong ammonia until slightly 
alkaline (the latter to precipitate out any iron present), set on the 
steam bath to settle, filter into a 400 ce beaker, wash the precipitate 
once with water, remove the beaker and dissolve the.iron hydroxide 
with dilute hydrochloric acid, catching the ferric chloride in a 
250 cc beaker, add to this filtrate 1 g of ammonium chloride and 
make ammoniacal, let settle, filter and wash thoroughly with hot 
water, catching the filtrate and washings in the original 400 ec 
beaker, reserved from the first precipitation. Add a small piece 
of litmus paper. Render the filtrate first acid with hydrochloric 
acid, then add 3 ce of strong hydrochloric acid, heat nearly to 
boiling, and titrate with standard ferrocyanide, as in standardizing 
that solution (see Reagents). Calculate total zinc as zine oxide. 

(ec) Orcanio Cotortne Marrer—(A. S. 7. M. Standards, 1921, 
p. 690).—Test the pigment successively with hot water, 95 per cent 
alcohol, alcoholic sodium hydroxide, and acetic acid. Chloroform, 
sodium hydroxide, sulphuric acid, hydrochloric acid-stannous 
chloride solution, and other reagents may be tried. The solutions 
should remain colorless. The presence of an organic color may 
often be detected by the characteristic odor given off on ignition. 

(f) Catcutations.—Add the percentage of white lead (see 
V 3 (b)), zine oxide (see V 3 (d)), and subtract from 100; the 
remainder is reported as extending and tinting pigments. 


4. LABORATORY EXAMINATION, READY-MIXED PAINT 


(a2) Caxine in Conratner.—Follow the procedure outlined in 
V 2 (a), noting that the paint should be no more difficult to break 
up than a good grade of mixed paint. 

(6) Weitcutr per Gatton.—Weigh a clean, dry, 100 cc diva dilibded 
flask. Fill to the mark with the thoroughly mixed paint and weigh 
again. The increase in weight expressed in grams divided by 100 
gives the specific gravity, which multiplied by 8.33 gives the weight 
in pounds per gallon. . 


SPECIFICATION FOR OLIVE DRAB PAINT 9 


(¢) Brusaine Proprrrms ano Time or Drytne.—Brush this 
well-mixed paint on a suitable panel, which may be ground glass, 
steel, or well-filled wood. Note whether the paint works satis- 
factorily under the brush. Place the panel in a vertical position 
in a well-ventilated room and let stand for 18 hours. The paint 
should be dry and free from streaks. Flow a portion of the paint 
on a clean glass plate. Let dry ina nearly vertical position at room 
temperature (65 to 100° F.). The film shall show no streaking or 
separation within a distance of 4 inches from the top. 

(zd) Cotor—Paint the sample and the standard on clean metal 

or glass so that the edges touch one another. Let dry and compare 
colors. 
_ (e) Warrr.—Mix 100 g of the paint in a 300 cc flask with 
7 ce of toluol. Connect with a condenser and distill until about 
©0 ce of distillate has been collected in a graduate. The tem- 
perature in the flask should be then about 105 to 110° CG. The 
number of cubic centimeters of water collecting under the toluol in 
the receiver is the percentage of water in the paint. 

(7) Voratie Turnner.—Follow the procedure outlined in V 2 
(e). Correct the result for any water found (see V 2 (e)) and re- 
port the remainder as volatile thinner. 

(g) Prercenrace or Pigment.—Follow the procedure outlined in 
Woe. (fs : 

(h) Testinc Nonvorarme Ventcrz.—Follow the procedure out- 
lined in V 2 (g), (2), and (¢), except that in the preparation of the 
fatty acids the mixture of paint and alkali is heated on the steam 
bath until all volatile thinner is driven off. 

(7) Coarse Particres anv Sxins,—Follow the procedure outlined 
in V 2 (4). 

(j) Txstrine Piement.—Follow the procedure outlined in V 3 (a) 


to (f), inclusive. 
5. REAGENTS 


(a) Uranyn Inpicator ror Zino Trrrarion.—A 5 per cent solu- 
tion of uranyl nitrate in water or a 5 per cent solution of uranyl 
acetate in water made slightly acid with acetic acid. 

(0) Sranparp Porassrum Frrrocyanmpr.—Dissolve 22 g of the 
pure salt in water and dilute to 1,000 cc. To standardize transfer 
about 0.2 g (accurately weighed) of pure metallic zinc or freshly - 
ignited pure zinc oxide to a 400 cc beaker. Dissolve in 10 ce of 
hydrochloric acid and 20 cc of water. Drop in a small piece of 
litmus paper, add ammonium hydroxide until slightly alkaline, then 
add hydrochloric acid until just acid, and then 8 cc of strong 
hydrochloric acid. Dilute to about 250 cc with hot water and heat 
nearly to boiling. Run in the ferrocyanide solution slowly from 


10 CIRCULAR OF THE BUREAU OF STANDARDS 


a burette with constant stirring until a drop tested on a white 
porcelain plate with a drop of the uranyl indicator shows a brown 
tinge after standing one minute. A blank should be run with the 
‘game amounts of reagents and water as in the standardization and 
in titration of the ue The standardization must be made under 
the same conditions of temperature, volume, and acidity as obtained 
when the sample is titrated. 

(c) Sranparpv Soprum TuiosuteHate Sorurion.—Dissolve pure 
sodium thiosulphate in distilled water (that has been well boiled to 
free it from carbon dioxide) in the proportion of 24.83 g of crystal- 
lized sodium thiosulphate to 1,000 ce of the solution. It is best to 
let this solution stand for Pycat two weeks before standardizing. 
Standardize with pure resublimed iodine. (See Treadwell-Hall, 
Analytical Chemistry, vol. 2, 3d ed., p. 646.) This solution will be 
approximately decinormal, dad it is best to leave it as it is after 
determining its exact iodine value, rather than to attempt to adjust — 
it to exactly decinormal. Preserve in a stock bottle provided with 
a guard tube filled with soda lime. 

(2) Srarcu Sorurion.—Stir up 2 to 3 g of potato starch or 5 g 
of soluble starch with 100 cc of 1 per cent salicylic acid solution, 
add 300 to 400 cc of boiling water, and boil the mixture until the 
starch is practically dissolved, then dilute to 1 liter. 

(e) Exrracrion Mixrurn.— 

10 volumes ether (ethyl ether). 
6 volumes benzol. 

4 volumes methy] alcohol. 

1 volume acetone. 

(f) Aqueous Soprum Hyproxipr.—Dissolve 100 g of sodium hy- 
droxide in distilled water and dilute to 300 ce. 

(g) Porasstum Iopme Sorurion.—Dissolve 150 g of potassium 
iodide free from iodate in distilled water and dilute to 1,000 ce. 

(hk) Hanus Soturion.—Dissolve 13.2 g of iodine in 1,000 cc 
of 99.5 per cent glacial acetic acid, which will not reduce ehyreanie 
acid. Add enough bromine to aouble the halogen content, deter- 
- mined by titration (3 cc of bromine is about the proper amount). 
The iodine may be dissolved by the aid of heat, but the solution 
should be cold when the bromine is added. 

(2) Axconotic Soprom Hyproxipr Soiurion.—Dissolve pure 
sodium hydroxide in 95 per cent ethyl alcohol in the proportion of 
about 22 g per 1,000 cc. Let stand in a stoppered bottle. Decant 
the clear liquid into another bottle and keep well stoppered. This 
solution should be colorless or only slightly yellow when used, — 
and it will keep colorless longer if the alcohol is previously treated 
with sodium hydroxide (about 80 g to 1,000 cc), kept at about 
50° C. for 15 days, and then distilled. 


SPECIFICATION FOR OLIVE DRAB PAINT Md bs 


(j) Stanparp Frrrous Suneware Sonvurion.—Dissolve 14 g 
of pure crystallized ferrous sulphate (FeSO,7H,O) in about 500 
cc of water to which 25 cc of concentrated H,SO, has been added, 
and then dilute to 1,000 cc. This solution should be freshly stand- 
ardized when needed, as it does not keep well. 

(4) Sranparp Porasstum Dicuromate Soxvurion.—Dissolve 
4.903 g of pure, dry, crystallized potassium dichromate in water 
and dilute to 1,000 cc. One cubic centimeter of this solution corre- 
sponds to 0.0108 g PbCrO,, or 0.0101 g PbSO,. This solution may 
be checked by determining its iron value on Bureau of Standards 
Standard Sample No. 27a, Sibley Iron Ore. 

(¢) Porasstum Ferrricyanwe Sorurion.—Dissolve a piece of 
potassium ferricyanide half as big as a small pea in 50 cc of water. 
This solution must be made fresh when wanted, because it does not 
keep. 

VI. PACKING AND MARKING 

No details. 


VII. ADDITIONAL INFORMATION 


This specification covers the requirements for a high-grade olive 
drab paint for outside and general. use. It may be ordered either in 
the form of semipaste pigment ground in linseed oil or of ready- 
mixed paint, and the purchaser shall state which is desired. 

The semipaste shall be purchased by net weight, and the ready- 
mixed paint either by weight or volume (231 cubic inches to the 
gallon). 

VIII. GENERAL SPECIFICATIONS 

No details. 


ADDITIONAL COPIES 
OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 
AT 
5 CENTS PER COPY 


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